Preponderance of the Evidence

This is the most common standard of proof you'll have to deal with. It is the one usually used in almost all civil cases. It basically means that "more likely than not," your case is the right one. That is not a huge margin; various examples have it put at 50.1%. I've also heard it said that if you had two equally balanced piles of sand and moved one grain of sand from one to the other, that will satisfy the standard. Either way, it's not an incredibly high standard.