Can someone explain Japanese particles to me?

Question:

Mostly が and は I have NO clue when and where to use them -.-

Answer:

I have no clue how to explain either. It's a really tough question to answer. No wonder you haven't got any answers yet. Truthfully I've been trying to answer your question for two hours now, but still haven't come up with any good explanation. The only one I could was that sometimes you can leave out particles altogether.

I'm an American. 私はアメリカ人です　or 私　アメリカ人です。

Either sounds fine. The second one might sound even better as spoken Japanese.