you can only do it thought matchmaking on double xp weekends or by hosting a custom game with your friends.
Halo Wars does have Xbox live.
Yes, definitely, on most playlists. Some single player (non-team) playlists do not allow it. Infection does though.
No, you can forge while not connected to xbox live. If you want to share your maps, and view other people's maps you will need xbox live though
Halo is only on the Xbox or the Xbox live.
yes the halo maps are free on xbox live.
no, you must connect to xbox live to download halo 3 map packs.
Yes. An Xbox Live Gold Subscription is required to play Halo 3's multiplayer.
No, you do not need Xbox LIVE to play any original Xbox games. Not all original Xbox games can be played, but Halo and Halo 2 do not need LIVE to be played on the Xbox 360. I just now tried it with my LIVE unplugged and signed in to an offline account and it let me play both of them. The previous answer was a lie, obviously.
obviously
You do NOT need Xbox live to play Halo Wars. Xbox live is only used if you want to play with other people and to update the game.
Yes, since halo waypoint is a downloaded application you would need xbox live to use it.
Yes, you can play firefight in Halo 3 ODST without Xbox live.