Hey, so I'm learning mastering but before I start the mastering process I'm struggling with a concept I cant seem to find an answer to. I know you need some headroom on all your tracks, I use logic and I set the dB to -6 on every track. Most often the synth or whatever sound I use will still shoot the dB level up over 0 dB on that track. Should I adjust the dB slider to whatever keeps the dB level around -6 when the sound is played at its loudest? or just make sure its set at -6 dB?

I feel like after typing this out I know the answer now but just to be sure... any thoughts? Tips? My last track had portions that were too loud when I tried to master it.

Also, before mastering the master track at -3 dB, can I make it -3 dB by adjusting the master slider or should the master slider be at 0 dB and the all the tracks feeding into it sum up to - 3 dB