As your dog learns more and more commands, you've got to start keeping track of what the commands actually are! Giving the wrong command is confusing to dogs, and when dogs are confused they usually will blow you off -- how are they supposed to do what you want, when you're not being very clear about it?
For example, "Down" vs "Off."
"Down" means to lie down on the floor/ground/wherever the dog happens to be at the moment. So if you use "Down" to mean "Get off the sofa," technically you're commanding the dog to lie down on the sofa. In fact you will see many dogs pausing momentarily in this situation -- your body language often says "Get off the sofa," but your words are saying "Lie down on the sofa."
Don't confuse your dog! The word is "Off." You can think of "Off" meaning "Four feet on the floor." So you can use it either for getting off furniture, getting off on your lap, or stopping it from jumping up on you. (Although your dog should be trained to not jump up on you in the first place; I can help you with that if you're stuck with a never-ending cycle of Dog Jumps -- "Off!" -- Dog Gets Off.)
Here's another one, that frequently confuses more experienced dogs and their owners. (Note: Depending on your dog, some of these might be slightly different, but this is the "official" way.)
"Leave it" vs.
"Drop it" vs.
"Give."
"Leave it" is a command that you use when you do not want your dog to interact with something, but the key is that you will give it *before* the dog begins the interaction. The correct time to give that command is right when the dog notices/orients to the object. So, the sequence is: 1) Dog orients to object/looks like it might grab it or go after it, 2) Cue "Leave it!" 3) Dog turns away from it/reorients to you, 4) "Good!" or "Yes!"/treat. Savvy handlers know the command works best if you use it right when the dog is first oriented to the item, *not* when it's got its mouth open to grab it.
"Drop it" is a command that you use when the dog actually physically has something in its mouth and you want to get it out of the mouth. You really really want the dog to open its mouth right then and there and drop it right out. Got it?
"Give" is a command that means you want the dog to drop the item, but you want it to drop it into your hand. The dropping-the-item is the same, but the location is different. "Drop it" means "drop it right where you are" and "Give" means "come to me and put it into my hand."
So, you see how complicated vocabulary can be. As your dog learns more and more, it might be helpful for you to write up a list of the vocabulary you are using, then check and double-check that you are not using duplicate words. The words you use as commands literally do not matter at all, except to you and your dog. Many people for example use "Out" to mean "Drop it wherever you are" and "Drop it" to mean "Drop it into my hand." The main thing is that you are very consistent with your dog. Because look at you and your fancy dog! You know you're doing well with training, when you actually have to step back and synchronize your vocabulary! Good job!