You've got 8 tracks to work with so ya need to space out your instruments and plan things a little better.

Try putting the drums in stereo on tracks 1 and 2.
Put the Bass on track 3
Put left and right guitar on tracks 4 and 5
Put vocals on 6
Put harmonies or synths on 7 and 8.
You can add a lead solo on one of the vocal tracks if you have one.
Once you've finished, go back and redo any tracks that need improving.

Try to add a little reverb to fill things out but avoid using it on the kick drum and bass unless you're going for effect cause it'll just muddy things up.

If you've got High Bandwidth, check out the multitracking tutorials on my lessons page. I've got a few where I used old 4, 8 and 16 tracks and described the process as it's going along.
There's also some info on using loops in combination with a drum machine so the drum tracks don't sound so cheesy.