Originally I did put the microphone right in the dome light by removing the piece of cloth from one the wholes near switch but I got a lot of complains from people that it sounds like I'm in a bathroom. So I ended up putting microphone with the clip near sun visor and now people saying they can hear me clear enough. I believe it is a quality of microphone that you get. I'm not 100% sure but I think Nissan was using actually 2 microphones in dome light to get a good sound but my microphone from pioneer avic-x910 could not work from there. You can run the wire behind speedometer then remove the cover on the left side and hide under white dash panel to the liner. Be careful with white dash panel next to the windshield....there's air bag inside and if you are planning to take it off it is a good idea to disconnect the battery and wait a little 'till it discharge completely.

Some people just drilling a hole either in empty slot like you should have next to mirror switch or right next to the dvd unit. Personally I don't know which location is the best but I didn't want to install mic into the dash:
