Some trainers who rely on less-modern methods can get caught up on the idea that dogs are "trying to dominate them" (as if these dogs have been working tirelessly in a bunker somewhere with maps & charts, hoarding a stash of WMDs or something...)
Example: Dog walking in front of you on-leash?...must be DOMINANCE!
...while that can be an example of dominant behavior, when a happy, healthy, and otherwise obedient dog does it, it's usually not about them trying to be dominant. Not at all. Sometimes a puppy wants to enjoy his walk, sniff the grass a little, wander off just a touch to investigate a butterfly... it can be harmless, joyful curiosity (rather than dominance.)
If your dog's behavior makes you fearful for any reason, the best advice I can give is to get individual, one-on-one help from a trainer. If it turns out that your dog is struggling with dominance issues, it's also helpful to try seeing the situation from the dog's perspective:
The truth is, most dogs really aren't trying to become some sort of family dictator. Dominant behavior is often simply a result of their survival drive. Dogs operate in a pack system, and they have a leader of that pack. In the wild, a pack without a leader is vulnerable and will perish. If your dog doesn't clearly recognize a leader in his family pack, he may begin to feel insecure, the survival drives kick in, and in order to ensure his survival, and the survival of the others in the pack who he loves, the dog steps up to lead. Quite often the dog doesn't even want to be the leader... it's a stressful job, afterall. More times than not, the dog is probably thinking "Why me? I really don't want to be the leader... but someone's gotta do it... OR WE WILL ALL DIE!" The motivation is innocent, but so much gets lost in translation.
Dogs who feel forced to lead a group of humans can get really stressed out. That stress can make an already insecure dog grumpy, impatient, bossy, rude, and sometimes even aggressive.
It saddens me to see these insecure, stressed-out dogs approached with harsh responsive methods that don't take into consideration why the dog is behaving the way that it is. By understanding why a dog does what it does, it helps so much! It helps soften our irritation, and lets us focus on solving the root of the problem. It's a very important first step in the process of fixing behavioral issues, and unfortunately some trainers skip right over it.
In the past, many trainers put their focus on providing quick fixes (such as choke or shock collar corrections, "alpha rolls," etc.) These scare dogs into submission. They can get fast, immediate results. But think about it...is it really a wise thing in the long run to poke and prod at a disturbed individual?... Whether that individual is a dog or a human...Most likely not! Wouldn't it be better to address what's causing all that pent up anxiety and stress?
In many cases, a key part of the solution is to beef up your leadership skills. Remember that dogs and humans interpret leadership in different ways. You may be a wonderful leader at work, amongst humans, but dogs speak a different language. There are lots of kind, easy ways to clearly, assertively communicate to your dog that you are the leader of your family pack. A positivity-based trainer can help you "speak dog" so that your pet will understand. My two favorite dog training book authors are Patricia McConnell and Victoria Stilwell, and their books both detail some of these leadership tips (see sidebar for links.)
Rather than trying to "put the dog in his place!" ...the ideal goal of these techniques should be to show your dog that he can have complete confidence in your leadership. If you are a consistent, strong-yet-loving leader, most dogs will then begin look to you for guidance, trusting in your abilities :)