Do you mean slide change animations and text animations? It all depends on what sort of powerpoint you're making and where you're presenting it. If it is a very professional thing, like for a job presentation or a meeting, I would minimize the number of flashy, annoying effects.
If it's a class assignment, you might have a bit more freedom to have fun and make it entertaining, but you still want it to be clean and easy to watch.
In general, don't overuse them. The animation features are there to make them more aesthetically pleasing and not so boring, but if you constantly have some sort of animation going on it's very distracting to the purpose of your presentation.
