It's nice to be able to reward your dog as often as possible. Treats are a nice way to reward them. It is best to give them smaller size treat more often, then bigger size treats less frequently. It is best to use them as rewards, it teaches them that when they are good you approve of how they are acting. Never reward a dog's bad behavior with a treat. If you feel the urge to give a treat for no reason, you can ask for the dog to simply sit to receive it. Treats are a good way of teaching dogs tricks, when they are successful praise them and give them a treat to let them know they have accomplished what you are trying to get them to do. But if they don't do the treat it is best to not give in and give them the treat, try and get them to do a different trick for the treat. Keep in mind it is not good to give table scraps as treats unless you want the dog begging every time you eat.
Dog treats come in many different shapes, sizes and consistencies. It is best when buying new treats to buy a small bag or box because your dog may not like that certain type or brand. Some dogs can be very picky. And then again, there are some dogs that will eat just about anything you give it.
Keep in mind that you do not have to give a dog a treat every time he does a trick, praise works very well too. You can alternate between praise and treats and simple praise.
Also it is not a not a good idea to give a dog too many treats, as it will ruin their appetite for the food that has the proper nutrition for them.