The call I get the most as a dog trainer is from frustrated owner's who are tired of their dog dragging them down the street when going for a walk.   Because the walk is such an unpleasant experience, the owner takes the dog on less walks, which increases the dog's excitement when it does get to go, which in turn makes the walk more unpleasant. It becomes a vicious cycle and both the owner and the dog suffer as a result.  
There are a multitude of training collars, leashes, harnesses and devices out on the market today that are supposed to make walking your dog easier.   I won't get into the pros and cons of each one of these devices on here, otherwise this post would be a mile long.  Training your dog to walk on a loose leash, with just a regular flat buckle collar is possible.  It has a lot less to do with the tool, than it does with your technique.  
If you have a puppy, get them used to walking around with a collar and leash right away.  Whether your dog is a pup, or a grown adult, start inside your home where there are as few distractions as possible.  Start to teach them to move away from leash pressure.  Wait for there to be slack in the leash and reward the slack with praise and a yummy treat.  Then let your dog go off exploring again. Once the leash becomes taut, wait it out.  Reward each time the leash becomes slack. It won't take your dog long to figure it out.  A tight leash, gets no reward, whereas a slack leash gets yummy treats.  Keep in mind what is rewarding, just being able to move forward is a reward for your dog, if the leash it taut, moving forward can not happen.  Ever.  If they pull...stop.   Wait for the leash to be slack and reward.  Turn around, change directions.  Be interesting to your dog.  Praise them and give them treats when they are walking beside you.  
Once your dog has mastered moving away from leash pressure indoors, take them out to the back yard and start all over again.  At first they may regress as there are a lot more interesting things to see and smell outside than there was inside your house.  Keep up the practice.  Rewarding the dog for walking beside you with a slack leash and not rewarding the pulling by moving forward.  Do not move on to a more distracting environment until your dog has mastered this technique in your back yard.  It is very important that while you are doing this training with your dog that you don't ever allow it to pull you on a walk. You will need to get creative with other ways to exercise your dog that doesn't involve walks.  
Once your dog has mastered the release of leash pressure in your backyard, move to the front yard.  Once that is mastered, take the walk on the road.  Just ensure that you continue to praise, and treat when your dog is beside you, and do not allow your dog to pull you down the road at any point.  If they start to pull, turn around and go in the opposite direction.  Walk briskly, stay interesting to your dog.  Be unpredictable, keep them guessing what you are up to and which way you will be going next.   The amount of time this takes to perfect, will depend on your dog and your consistency.  If your dog has had years of dragging you down the street, it is still possible to change that habit into a calm, relaxed, engaging walk.   One in which both of you can enjoy.  

Whether your dog has one specific fear, or if they are seemingly afraid of everything, there are some steps you can take to help calm their minds and make their lives more enjoyable.  Let's start at the beginning. 
There are a few common causes of fear in dogs...1) genetics- some dogs are just naturally more fearful or sensitive than other dogs due to their genetic makeup. 2) Lack of early socialization- the amount of positive socialization experiences your dog requires in the early stages of its life will vary from one dog to the next. Some dogs are just more easy going and extroverted, so they do fine with minimal exposure,  while others are more sensitive and will require much more positive exposure to many different stimuli throughout their lives.  Emphasis on the positive exposure.  Making sure the experiences are good experiences are key to socialization.  3) Learned behaviour- a bad experience can teach a dog to be afraid of a certain item. It could be something as simple as a car backfiring upon their first interaction with a man with a beard.  The dog may then associate the man with a beard with a large scary noise.  (It's not always this simplistic, of course).  Finding the root cause of the fear is not always possible.  The most common misconception is that the dog must have been abused, so that's why its afraid all the time. Or my dog is afraid of men, so a man must have abused it in the past.  Although, that may very well be a possibility, 9 times out of 10, it isn't the case at all.  
So what can you do about it....work on positive exposure to the fearful stimuli, while keeping your dog under threshold. Desensitizing your dog to the stimulus that scares them. Keeping them under threshold is key.  What is threshold? Basically the dog's threshold is the point where your dog is reacting and no longer thinking. You won't be able to help your dog when he is in this state of mind.  Don't allow them to get to that state.  The more opportunity he has to practice the fearful behaviour, the more it becomes an ingrained habit.   Instead, you need to stay at a distance from the scary thing, allow your dog to look at it, get their attention back on you and reward your dog.  With repeated trials, he will learn that the when the scary thing is around, if I look at my owner instead, I will get a treat.  Pretty soon, the scary thing will mean good things and their fear will decrease.  Of course, this sounds very simplistic and there is a lot more things involved in the process, but this gives a general overview of the goal. 
What if your dog is seemingly afraid of everything? Break it down and work on one thing at a time.  Don't try to work on everything at once or you will set you and your dog up for failure.  You will find that your dog will gain confidence as you work through their fears and the scary things will become less and less scary.  Work on obedience command training.  This increases your communication skills with your dog, which in turn increases your dog's confidence and its bond with you.  Stick to routines. If your dog knows what to expect on a day to day basis, they will feel more secure in their environment. Learn to read your dog's body language to ensure that they are kept under threshold.  If your dog is severely anxious, and not able to get under threshold, medication along with the desensitization procedure will give you the added assistance you may need.  Fear is not something that you can overcome in one session, but if you put the time and effort into training your dog, he will reward you tenfold.  Seeing a dog transform from a scared, anxious dog to a more happy, confident dog just warms my heart.  

No other command training is quite as important as the recall or "come" command. If your dog darts out the door heading towards a busy road, you want to have the control to tell your dog "come" and have them immediately stop and come running back to you. It can literally be the difference between life and death.  Start training the "come" command as soon as possible, making it the most rewarding experience for your dog.  The 3 things to remember are 1) Don't ever call your dog to come and then punish them.  No matter how upset you are that your dog just chewed your $100 shoes, do not call them to come and then yell or punish them.  Your dog will just learn that coming is not a very pleasant experience.  2) Don't ever call your dog to come to you to take away their fun.  Say your dog is playing in the backyard or at the dog park and you call him to come because it is time to go.  You are taking him away from all the fun he was just having.  Instead, practice calling him to come, give him a treat, and let him go back to playing.   Repeat this over and over, so that 9 times out of 10, "come" means he gets a treat and then gets to go back to playing.  As long as the majority of the time it doesn't end the fun, he will more likely listen to the "come" command.  3)  Don't ever call your dog to come if you can't enforce it. This is very important as you are proofing the behaviour.  Keep your dog on a long line/leash and if he doesn't come when you call him, use the leash to reel him in.  Still give him a reward, maybe not the jackpot reward that he would have gotten if he came to you on his own, but still give him a reward.  You don't want your dog learning that he can choose not to come to you if something more exciting is going on.  Don't forget to praise, praise, praise your dog when he comes to you. Reserve a jackpot treat for the come command. Make sure he only gets this jackpot or favourite treat of his when he hears that magic word "come".  Any other command training that you do with your dog will still get a reward, but this special treat is only given with the "come" command.  If you follow these tips, you will have a reliable "come" command when you need it the most. 

Training obedience commands such as sit, down, stay, etc, can seem like cool tricks and not necessary to some people, but it is a lot more than just cool tricks.  Obedience command training is important for all dog/human relationships.   It not only enhances communication with your dog by increasing their vocabulary of actual human words, but it also teaches them the subtleties of communication.  By learning appropriate vs inappropriate behaviour, they learn how to coexist in your household. Human rules, generally go against the natural behaviour of a dog and this is where the majority of behaviour problems come into play.  Jumping up, barking, exploring things with their mouth, digging...these are all natural canine behaviours.  The problem arises however, when we ask them to come live with us in our homes.  We therefore need to find a way to communicate what is or is not acceptable under our roofs.  Obedience training gives us this form of communication. 
     The time spent training your dog enhances the bond between the two of you, which leads to a happier dog and of course a happier owner.  Take the time when your dog first comes home, no matter what age, to show them what you want.  Dogs are learning every minute of every day, it's up to you to teach them what you want them to learn. You have an average of 10 years to live with your dog. Why not make the most of the experience.