Hang out near or in the pubs and bars. You'd be surprised how many turn up in the middle of the day after their midday training sessions.
Or sit in the hotel lobbies and read a good book. You never know your luck. A player might just come along and sit right next to you.
Watch them on the practice courts. Pay keen attention. After they're done, compliment them on a stroke they appeared to be hitting well. Sucking up to them helps if you want to get into their good books. Then you can start up a conversation. Even if you can't tempt them with a free dinner for that night, you'll have spoken to them at least.
Visit some of the tourist attractions in the city of the tournament being played. Some players like to go sightseeing during their days off, or if they lose early. It's rare that they'll train all day every day. Sometimes they'll take one leisurely afternoon or morning off from training.
If you see any of their entourage, approach them too. Chances are, they're more likely to have a chat with you because they're not the ones who have to train or compete so they're not in a hurry to get anywhere. Who knows? If you make a good impression with them, they might just introduce you.
Some DON'Ts: Never approach a player after they've lost a match. They're usually in a grumpy mood and will most likely want to hit the nearest thing that gets in their way.
Never stare at them for longer than 2 seconds. They might think you're a stalker, or they might feel uncomfortable. That's not the aim if you want to meet them.
Never try to meet players in awkward situations such as in a restaurant (they might be very hungry and ready to snarl at you over the last dessert cup), in a restroom (they might be busting or feeling ill and you don't want to be the obstacle in the way of keeping their underwear clean) or when they're trying to receive medical help (they might be in pain and more likely to snap at you).
That's all I can think of right now. Oh yeah, one last thing. If you act like you're not quite all there in the head, but appear friendly enough, they'll become sympathetic to you and treat you like a best friend. Ensure that you have someone with you who can pretend to be your minder or caregiver. If you're in a wheelchair, that's a bonus point. Able-bodied athletes can usually appreciate those less able-bodied than themselves and are more likely to give you their time in that situation.
Caution: Only use that last suggestion if you're desperate and only as a last resort. Not recommended if you're not a good actor or have a conscience about lying.