- Melee Status
Before you do anything else, go to "Map -> Map Status" and see if it is "Melee" status. If not, the dialog will tell you why.
- Player Settings
You'd be surprised how often this slips by while folks are crafting beautifully-textured smiley faces on their maps. Go to "Map -> Player Properties..." and check this dialog carefully. By default Player 0 is "Neutral" and Player 15 is "Hostile," which is what you want for a melee map. Then make sure Player 1-# are set to "User" where # is the number of spawns on your map.
- Team Settings and Disabling 1v1 Spawns
If your map is for teams (2v2, 3v3) or if it is supposed to work like Shakuras Plateau where you want certain spawn pairs to be disabled in 1v1, you need to visit "Map -> Team Placement..." and use basic mode for setting up team games and advanced mode for disabling spawns in 1v1. Open Shakuras Plateau in the editor for an example of configuring 1v1 spawns.
- Game Variants
Go to "Map -> Game Variants..." and check the box for "Use Default Variants" and melee game-typey stuff will appear. If you can't seem to get refs or observers in your map, this is probably unchecked.
- Unpathable cliffs
Did you use strips of high ground around the edges of your map, or maybe put some tiny unpathable cliffs here and there? Did you either use pathing blockers (doodads) or the pathing fill point or the paint pathing layer to make them unpathable? If you have a pathable cliff above the main and you didn't mean to, your map might be arrested for abuse.
- Unusual Pathing/Cliff Pathing
This is a subtle issue. Sometimes you want a doodad that doesn't have a footprint to be in the play area so you paint some pathing on it, or do cute stuff with pathing blockers here and there. If you have anything like this on your map, place a big group of marines and a big group of reapers on the map and fire it up in test mode. Then walk giant blobs of units all next to and around and past the tricky pathing areas to see if anything unusual behavior occurs. Do the same with the reapers, sometimes when you monkey with pathing near a cliff the cliff-walking units can get into places you didn't think they could.
- Generate Lighting Map
You want to generate this so your map will have better lighting in the SC2 engine, but you wait until the terrain layout is set, otherwise you have to regenerated. Go to "Data -> Generate Lighting Map..." to kick it off.
- Generate Foilage
Did you forget to plant bushes? Go to the terrain control dialog, click the tree icon and click "Generate Foliage" to make cute plants appear. I usually erase the foliage layer completely then just paint exactly where I want it.
- Publish "Public"
When you go to publish a map the default for "Release" is "Private" which means people cannot find your map by name when the search for it. Switch to public when it's go time.
- Test Games!
Last of all you can easily double-check everything else you've done by playing games online with other people. Creating games, joining them, having people search for the map, having observers in a game will all tell you your map is configured for release. There are many chat channels where you can recruit some nice people to give you a hand, like 'MotM' for instance.
Please post other items for this checklist so our maps will shine.