This is down to EQing everything properly. Thinner guitars, like Clayman for example, require a huge bass tone to make up for 'em and vice versa. Same goes for the drums, you always gotta mix in regards to the big picture. I started out with this EQ guide : http://noise101.wikidot.com/eq-guide and then managed to know the frequencies and to remember them. Just go with your ears and try not to mix too much with headphones if you're doing so, usually they're more coloured than nearfield monitors and they can sound too large for your speakers' good. Even though you'd like it to sound more centered.