Generally the best spots are by teleporters, such as on Cold Storage and at the top of a lift.
Many spots can be found with a quick search on YouTube.
Slayer DMR's on Countdown or SWAT on Powerhouse it's the best maps and game types around.
Whether a map is good or bad really depends on the players preferences. I personally like Haven, Adrift, Abandon, and Complex. For Big Team Infinity Slayer (there are different maps) I like Ragnarok (the Halo 4 version of the popular Halo 3 map Valhalla) and Exile. I don't like Meltdown. I don't really know why I don't like it though. For most game types, Haven is the best (Slayer, Flood, SWAT, etc.).
The answer to the question where the best camp grounds for the camping holidays are, according to my research, California and Hawaii has the best camp grounds for camping holidays.
That depends on who you are, and what, and where you like to do and go. But i think that the best place to go camping is Utah.
halo 3 odst
There is no best in Halo 3. There can be a team that is the best, but know single person is the "best".
halo 3
halo dev trainer
Halo 3 is by far the best yet. i say halo reach! I have to say reach is the one i enjoyed the most.
Cause everything is with live, the best games are halo 3, halo Odst, halo reach and that is a about it
Halo 4
There is no specific place you train slayer. You get a quest, and go where the monsters are that you are supposed to kill.