AndroidGuys has put together a list of tips to keep your Android phone optimized. 

This is simply a general list of things that I notice on new users’ phones that really brings them to a stand-still. (Especially when you are guilty of all of them at once!)  I understand that everyone’s experience of their Android phone and what they use it for is different; however, the more you give your droid to think about at once, the less efficiently it thinks.  If you remember this very general rule, you are most likely going to be able to trouble shoot or tweak things on your own to be back in tip-top shape in no time.

He is absolutely right. I have seen this a few times already, phones overloaded with applications that I call vampires because they suck all the resources available in the phone.