Timing
Timing is super important. Remember your puppy or dog has a very short memory span. You must praise your puppy in the moment she performs her task. Find out what reward your puppy values most, usually a treat and give it to her right when she sits, comes, eliminates or whatever else she has accomplished. If you wait and do reward her after the fact it will provide confusion for her as she will think the reward is related to something else. The same is true with discipline. Make sure to watch your puppy closely and when she has an accident in the house catch her in the act and tell her no and scoop her up and take her outside. If you wait and discipline her later when you find an accident in the house, she won't understand why she is being punished and again this will cause confusion for her.
Inconsistency
Inconsistency is a huge training mistake. There are a number of ways to be inconsistent with training. Many people allow their puppies to jump up on them when they are little puppies, but then they want their puppies to stop jumping when they get bigger. Some people won't allow their puppies on their bed most days, but when their spouse is out of town they want their puppy to sleep with them. Try to always put yourself in your puppy's shoes and try thinking about your rules. Would they be confusing? Or are they super clear and consistent all of the time? This doesn't mean that you can't start or change rules. Try to think things through as much as you can and then consistently teach it to your puppy. The earlier and more often you teach your puppy the easier it will be.
Divided Attention
We are all guilty of this one from time to time. You want your puppy to sit but you're reading through a text and are having a hard time doing both. You'd like for your puppy to stop chewing on your blanket, but your in the middle of your favorite movie. Try to put your device down or press pause on your show and focus for those few seconds with undivided attention on your puppy. You will be far more effective and your puppy is way more likely to respond to you.