Well, I suppose you could sneak into his room at night, alone, and perform some questionable acts and see how he responds... :rolle: Please note that the above ^^^ was 100% a joke answer. Don't try that. It's a surefire friendship-ender and quite possibly illegal (depending on how you swing it). Seconded (serious answer). That's the only way you can really know.
I think you should try with the always useful "Truth or Dare" game. A little late in the game try asking him things like "Have you ever been attracted to a guy?" or "Have you ever kissed a guy?" and see his reaction. You can always tell him you're running out of questions if he starts to be suspicious. Good luck!
that's not a good indicator at all. there's plenty of closet cases that know how to act straight. it's very easy to look at a girl's boobs or ass when she walks by, check her out and acting like you're enticed by it when you're geniunely not into her at all. all i have to say is either ask or just pay close attention to him.
depends... do you want to go to jail for sexual assualt, or not? if not, never be afraid just to ask. Don't be flirtly or playful, just be casual.
I think we're forgetting here the OP never really explained why he thinks his friend is gay. John, exactly why do you think this? Are you just hoping or have there actually been signs? If so, explain to us.
Be honest and real with him. Tell him about you to lighten the mood, and then ask him in complete confidence if he is or not. If he's a good friend, he'll understand and accept you, and he'll know you'll accept him if he is indeed interested in the same sex. Don't be rude, pushy, impatient. Just be very honest about it, and 100% true to yourself and him.