When you're setting the gain on your amp, the best to tip to keep in mind is that "you always need less gain than you think you need,". Go easy with the gain and if you think you're lacking distortion, whack your strings harder, you'ill be surprised how musical your guitar and amp could sound.

Yup, that's true ... .

I have seen alot of noobs, first time on stage go and put the Gain to 10 . He thinks more gain more cool  ... my ears was like 

Exactly, worse if they're using Boss distortion pedals (*Ahem* Metal Zone), ear-piercing and fizzy. 
Yup, more gain also means less clarity and more compression.
If you substitute the gain with volume, you'ill get a bigger sound with clarity to cut through the band. What sounds good in the bedroom doesn't necessary sound the same live.