People who do not believe in God don't want any proof. You can't even talk to them. They don't want to hear it.

So here's what you do:

Most people who do not believe in God believe in evolution. Show them that evolution cannot possibly explain everything. While there can be no actual proof of God (short of seeing Him in person some day), it IS possible to disprove evolution. Find a few counterexamples, make your friends reconsider their basic assumptions, and they may reconsider the possibility of God.

As Spock said on Star Trek, "If you eliminate the impossible,...