It has to be natural, first and foremost. If the guy likes you chasing him, that's fine. If he's more "traditional," he may want to do the chasing. This is where you feel people out. Find out what he prefers. If he's interested in you, he will probably appreciate you making the first move (guys get tired of always having to pursue). If he's not interested, he won't be pleased. I am also of the "old school" I always let guys pursue me, because that way I could be sure they liked me. But I've talked to quite a few guys who said it was a nice change to sometimes have the woman be the aggressor. Say something, then let him take the ball and run with it. Some guys need a little push if they're shy. But there is no set "formula" as has been said. Each situation is different, and requires diplomacy.