Hello Guys. So i'm making a movie.

I make my own sounds, then some women in the internet are also helping me and send me their own sounds, then i also grab high quality audio clips from the web . 

What i end up with is sounds that have varying degrees of loudness and depth. 

Last time when i made a movie, the sound ended up horrible because at times it was too soft you couldn't hear it and you had to switch the volume up and suddenly the sound would get louder and OUCH i would have to cover my ears. 

This time i don't want to make that mistake. I do have Final Cut and also a program Called Soundtrack for Mac. I'm sure i could do sound editing at the end when all my movie is done, but anyone have experience? any tips?