The three I've heard most often are:
- The evidence of creation. Look at the world - its pretty amazing isn't it. That couldn't have happened by chance could it?
- The evidence of selfless people. There are people who have done amazing things for other people and got nothing for themselves in return, that shows there's a God, doesn't it?
- The evidence of the bible. The bible says that Jesus died and rose again, there are no first century documents disputing this, therefore it must have happened.
And just because there are selfless people doesn't mean that there has to be a higher selfless being. If that reasoning worked then the existence of a higher selfless being would have to imply the existence of an even higher selfless being, and so on.
And there doesn't seem to me to be any point in trying to prove the historical authenticity of the bible in an argument. The events are so long ago in the past that they are beyond the reach of convincing historical certainty. Sure, the events might have happened, but you cant prove anything.
Why do none of these people use contemporary evidence? If there is a God who wants to interact with people today, then surely that interaction can be observed and experienced. If it can't then there is no reason to believe, if it can then everything else falls into place.