Professional sound does tend to require professional expertise, so it'll be sort of hard to just tell you what to do. But here are some pointers I think will help a lot:
- In post production, don't be afraid to re-record any audio (especially dialog) that didn't come across good the first time. This is done routinely in feature films, etc, it's not "amateurish" to fix your problems.
- Concentrate on recording dialog when you're shooting, not ambient noise at the same time. So turn off anything that's loud on the set that could get in the way of dialog.
- Then mix ambient noise in during post, so that it's completely separate from your dialog recording so you can control the levels separately. During this time it's good to foley things like footstep noises, turning doorknobs, pressing buttons, etc. It really adds to the overall feel of the film.
Equipment-wise:
- Quality will
partially depend on the quality of the mics you are using. I agree a "boom" mic (which is a shotgun mic on a boom pole) would be good. Shotgun mics are hypercardioid, meaning you have to have it pointing right at the audio source in order for it to be picked up, and it's telescopic so you can have it farther away.
- Get your microphone as close as you can ("proximity") to what you're recording.
Good audio takes practice, and it's even hard for professionals to get right sometimes. Do your best for now until you get your hands on some (hopefully) good equipment in film school.
Oh! And be sure to take lots of audio classes! People tend to focus on video/film production and never really learn how to do good sound. So paying attention to audio will make you a huge asset to production companies!