| First, try to think of it in "3-D", with Frequency as up-down, Presence as front-back, and Pan as L-R. Frequency is generally set by the instrument (and EQ), Presence is usually controlled by atmospherics (i.e., volume, Reverb, EQ), and Pan is, well, Pan. Position each instrument in space (on paper, even), then use the mix options to fit that position, giving each instrument some space.
If the drums are a stereo mix, spread them across the Pan. Usually fairly Present in rock
Consider bouncing/copying the ryth track onto a second one, and apply different EQ/FX to make a slightly-different version, then you can pan the ryth tracks L and R to spread it out. Softer, maybe some verb to take them out of your face when the lead guitar is hot.
Use your EQ to keep the guitars off the bass, and to separate the bass drum and the bass. Bass is typically centered since low freqs are non-directional, but this is also an artifact of mastering discs and is not required in most cases unless you're planning on pressing to vinyl.
You can often bring the lead guitar very present by centering it in the mix (mono) and drying it out, yet having the results of the FX (chorus, 'verb, whatever) go stereo and get panned off-center to fill the sonic space.
I also do quite a bit of "hand compression" using the automation in Cubase to run the gain on the track up and down based on the current mix, bringing up ryth guitars between the words in vocals, pushing them down (and boosting the lead) during leads, etc. Same with drums when you need a strike to really punch through. Tedious, but well worth it.
There...the 3 minute primer...FWIW/YMMV | 
and the guitars are leveled out so the lead is present more so, but not completely over powering the rhythm.
