If I want to use a shotgun mic for a Nikon D90?

I've never had to use an external mic for a camera before, as I usually make music videos, and don't need to record an higher quality audio. What will I need to get for high quality sound, and what would you recommend (if anything) I buy with the shotgun mic?

Added (1). I know the D90 lacks the right connection, but would I be able to connect the boom mic to a laptop or another device?

Unfortunately, the D90 does not have an external mic connection. You have to remember, the D90 was the first DSLR to include video, so it only had basic features.