How old is your toolbox? If it's old, it probably has a lot of tools in it. Indeed, you might find that it's so full, you've switched to a truck to carry your various props. Some of your tools are surely tried and true. You've met the goals you set out to meet using them and quite possibly reached some very nice success. Success, security, knowledge, admiration from others - as humans we need these things.
Your toolbox likely carries physical props (treats, toys, special collars, sticks, etc.), information (solutions to specific problems), cutting edge options (highly adjustable e-collars, remote ball launchers). and "common knowledge" for your sport ("your dog MUST perform", or "it's always the handler's fault").
If you've been around awhile, odds are excellent that you've invested a good deal of time, money, and emotional energy building up your toolbox. Odds are also good that you haven't thought too deeply about what you have and why you have it.
If you're getting queasy, you can relax. I'm not going to question your beliefs about the need for a prong collar or how many cookies you use in a training session. I'm not going to ask you to look at your physical tools or choice of training techniques. I'm going to start with a simpler and less threatening query - specifically, when was the last time you took a good look at your "common knowledge" about dog training? Not necessarily with an eye towards changing, but with an eye towards ensuring that your common knowledge is still compatible with your current training methodology.
I'm going to mention five pieces of common knowledge that I lived with for many years and that I have since thrown out. Maybe you'd like to play along and see where you stand as well.
1) Do not feed your dog before a trial.
a) My food driven dog gets frantic when she misses a meal, my "routine driven" dog vomits bile, and I know that for myself, my mental capacity is reduced when I'm distracted by hunger. So why is it that my dogs did not eat before trialing for close to 20 years? Because I never bothered to think about where I had received that information and whether or not it made sense in my circumstances; I simply did what I heard because it was standard practice - common knowledge. Personally, I don't care if you feed your dog the morning of a trial, but you might want to consider what your practices are, and why. What makes sense for you and your dogs?
2) End training on success.
a) My dogs live to train. Love to train. If I ended when they were doing it right, they'd be punished for figuring out what I want. That's silly. Once upon a time this approach made sense, because training was quite unpleasant for the dog, so all the dog really wanted was to have the misery end. But if your dog loves working and training, then "ending on a positive" just doesn't make much sense anymore. Personally, I tend to wait until my dog gets distracted or sniffs to end the session. Now the mature dogs don't normally make mistakes in training, so I end when I've had enough. The days of escape/avoidance training are long gone for me. What makes sense within your training system?
3) Always precede a command with the dog's name.
a) This made sense when dogs did not pay attention to their handlers. It was a warning - "fido, heel". If Fido woke up on his name then he avoided a correction. If not, then Fido paid the price. Indeed, it was a kindness - a way of allowing the dog to avoid a correction. But if your dog pays attention because it is impossible to perform correctly without attention, then why are you using their name? When you are directing another person, do you precede each request with their name? Not only is it a waste of time but worse, it teaches your dog to simply ignore the first second of each cue you give. Does it cause great harm to use the name? No. But consider why you do it - maybe you have a good reason, like training multiple dogs at the same time. Just think about it.
4) Don't let your dog sniff.
a) Dogs like to sniff. Personally, few things are more irritating than listening to a handler command "leave it! Leave it!' every 20 seconds. Why leave it? Why do you care if your dog sniffs while you chat with your friend? Sniffing is not the first step towards canine world domination, nor is it the first step towards sniffing during heeling in the ring. For Pete's sake; you're not heeling; you're standing around talking to your friend. Dogs use their nose to examine their environment in order to feel safe and to be able to focus, much the same way humans use their eyes to take in a new environment. Physically preventing your dog from sniffing doesn't make your dog not want to sniff. It makes you an irritation that your dog will wish to get rid of - so he can sniff. All of my dogs sniff, and not one time, not once, have I had a dog sniff in the competition ring. That's because sniffing is an incompatible behavior with working, and I focus on getting what I want, not what I don't want. Is it ok if your dog sniffs? Think about it.
5) Don't let your dog get away with any failure to perform.
Seriously, who cares? So your dog failed to do something. You'll get a lot further in your training if you figure out why your dog would not or could not perform than if you focus your energy on the behavior that didn't happen. Sometimes my dogs don't want to do something. Maybe they are experiencing physical pain. Maybe they aren't sure how to perform. Maybe I'm a dead boring trainer and I cannot motivate them to care. Regardless of the reason, "making" them perform probably doesn't progress your training goals, and it certainly doesn't progress your relationship. At most, it makes you feel like you're doing something, but doing something and training your dog don't have a lot in common.
The more I examine my beliefs, the less common knowledge seems to make sense for me. As I shed my common knowledge, I find myself freed up to focus on what does matter - developing a training relationship that works for me and each specific dog, regardless of what my friends or fellow trainers might find works for them.
Anyway, give it some thought.