Depends on the amp.. On most cheap amps I have the gain pretty high but on a decent amp you really dont need (or actually shouldn't) turn the gain all the way up
I put the gain from a pedal(mine's Korg AX3000G) and as it has a nose gate to reduce the noises coming from the picking(everyone produces them doesn't mind how good you are,Jhon Pettrucci,Stev Vai,Alexi,etc...al of them do and have noise reducers)I put the gain a bit over 7/8,but with any delay or chorus because then or I put down the drive at 4 or 5or it sounds like shit.btw amp and guitar have something to do with noises also.my guitar is not one of the best(Ibanez RG370DX),but when I change to the old one the difference is easy to notice,and playing with a 10 W Academy or Behringer or whatever is not the same than with a good head and a good cab.bt anyway the mos important thing is the player:if player is bad,it's gonna sound bad,LOL.