I would read John Purcell's excellent book on Dialogue Editing:
https://www.amazon.com/Dialogue-Editing ... 0415828171[I'm quoted a couple of times in the book, but don't let that throw you.]
Dialogue and sound editing is really hard and requires great instincts, nerves of steel, lots of experience, plus a quiet room and great loudspeakers. It also helps to have tools like iZotope RX (and possibly the Waves plug-in package plus some good reverb plug-ins). Purcell's book gives some guidelines on what to do and what not to do, and one of them is always leave one copy of the sound completely untouched, so that you have a "processed" version and an "unprocessed" version available in case your final re-recording mixer needs to compare them. (If you're doing the final as well, then different concerns apply.)
It also helps to understand different kinds of microphones, so if necessary you can re-record the dialogue later on (ADR) and precisely match the mic as well as the shooting conditions for worry-free editing later on. It's a complicated subject.