Many people (including me) have had problems with Halo: Reach and maps. I have the 4 GB console, but when I play Halo, it says I don't have a hard drive which means... I can't get any maps from Bungie.net. There is a solution!
Step 1: Requirements
1. Halo: Reach
2. A friend.
3. 5 minutes at most.
Step 2: Part 1: Gamemode
This is the easiest step out of the two.
1. Have friend go in to custom games and set up the game type to what you want.
2. Once it is loaded, back out until you are hosting a custom game.
3. Then go into the game options menu and press X to save game type.
4. Save as whatever you want.
Step 3: Part 2: Map
This is the hardest part for most people because it requires Forge mode... And most of the time, it's hard making someone go to that.
1. Make friend go to Forge Mode.
2. Make him/her select desired map.
3. Load map and play.
4. Press start and choose option "Save map as new file..."
THAT'S IT! You now have the gamemode and map. Repeat for any other things.