I agree with all that has been said - you can never force anyone to believe in God or anything else for that matter.
If someone is genuinely seeking for God, then one of the ways they often find Him is through others who believe. I've never heard of anyone coming to a believing faith by being hit over the head with a big stick and harangued with Bible verse after Bible verse, but I've known many people drawn to faith by the love, kindness and concern of other believers.
So if you want someone to believe in God - let them see what He looks like in you and maybe that'll start the ball rolling.