Don't offer any more money than he's content with. Typically what happens is he'll say he's thinking about it, come back a week later asking for more money, then sign when you increase your offer to whatever his new demands are. Obviously folks will be able to come up with plenty of examples where their "undecided" guy didn't sign, but I've maybe seen 1 out 15 or 20 that I've had that didn't eventually sign.