That's a simple audio question and there is an audio guy in the forums able to answer this better than I can.. but I'll try at it anyway.
When you first get to a location, your audio guy should take... cannot remember the name, but its like a baseline recording of your background audio noise.. That way your audio editor is able to plug that into his software and use it to match and eliminate the background noises. I'm not talking the person yelling during your take, but the constant humming of a fridge, a computer fan etc.
Directional microphones, ADR and foley is also something you might need to consider.
For distribution, you also need to consider another issue. If you intend on selling foreign rights, especially to non-native speaking countries than your own, you'll need all dialogue on a separate track. That way they can wipe that track and dub in their own language.