What is proper Xbox live etiquette?

    Is there some proper finishing school on how to decently behave on xbox live that people have yet to take? I'm not asking about the obvious timmy situation, for me, that has mostly been avoided by joining this site. Here are the most recent problems and concerns I have run across;
    I'm currently in 2old2play's GSN 2old2puck NHL 07 tournament. Things went pretty well until it came time to get the last  two of my regular season games in (I'll not use names here, because if the people in question are reading, they'll know who they are, and there's no need for libel). I contacted the owner of that team on several occasions, even going to the extent of setting up a lobby room, leaving him a message, waiting, watching his gamercard, leave another message, see him play another game against the computer, leave another message, wait, see him start yet a third NHL 07 game against the computer, then see him log off. Never once did he reply. I did this routine twice, then a third time I only waited for him to finish the game he was playing, after which he logged off. In addition to this, there were a few times where I could see from my pc that he was on, so I'd send a text message, courteously, of course, and not get a reply. So, he ended up missing a bunch of games, and missed the playoffs, without a word from him. He was the third member of the tournament to leave in such a manner, I believe.
    So, now the playoffs have started. I think a lot of us are excited to get this tournament done so that we start a second and do it up the right way.  To start a second, you must finish the first, though. My playoff round one opponent, whom I should say that I had no problems meeting up with in the regular season, is now starting to exhibit similar behavior, to a lesser degree. Twice now I've left a message, one voice and one text from the pc, only to see him log off about an hour later without a reply.
    What is the proper etiquette to use in this situation? Do I continue to bombard this person with desperate pleas to play our games in a tournament he signed up for? Do I wait for him to initiate the game on his terms? I know I sound like a character from one of those sex and the city type of shows, but I'd really hate to win my playoff games just on forfeit. I'd honestly settle for a quick little reply, even along the lines of, "sry not 2nite" (as much as I loathe text speak). All I get is nothing. Should I whine to the tournament organizer?
    That first incident might have been avoided by using a guideline I've now suggested for tournaments; Minimum number of posts for participants. Meaning you've got to be an active member of the site to participate in the tournament, or have a current member vouch for you. Last thing on this particular topic; if you're reading this, and fear I may be talking about you, you're probably right, but know that I'm not pissed or angry, just a little baffled at the lack of response.
    The other thing I've come across is joinable games. What is the proper or acceptable way to join someone on your friends list when their in a joinable game? Crackdown, I feel, is really touchy, because it requires the joinable person to stop what they're doing. What about Worms, GoW, or CoD3? Should I send a 'heads up' message that I'm going to join them, or asking them if I can join them? Cod3 is pretty easy, because if they're joinable, it's not ranked, and there's room for more. Gow almost as easy, but then there might only be room for one, and they're waiting for someone in particular. Worms is tough, because they're only joinable while setting up a player match game, and perhaps they're doing t to only include the maximum of 3 others.