So many tips & trick that you'd be better off looking for a book or two.

However - The most important thing is that the raw tracks have that open airy quality to them. Dull sounding guitars aren't going to give a nice, wide sounding image no matter how they're panned. Drum overheads with a narrow, but realistic X-Y image will sound open and wide when panned IF they sound really nice to begin with. Again, it comes down to the sound being recorded. To harsh, it collapses. Not bright enough, the image seems too narrow.

Same thing with compression - used judiciously on certain sounds, it enhances the apparent stereo image. Too much, and it makes it unnatural and unsteady.

Great sounding instruments panned "naturally" tend to have a great and natural sounding stereo image.

how about stereo reverb -do you use it at all?

Quality Analog to Digital converters also have a big effect on the largeness of the signal that the recorder catches. Preamps with transformers also produce a larger image in my experience. Arrangement is also an issue and appropriate use of panning... making use of the center channel and the near center area so the wider panned stuff sounds a bit more separated from the closer to center stuff. Just my $0.02 But like Massive Master said, there are a lot of tricks...

well i never did recording for live drum sessions so can't give you a tip regarding that but for the guitar you need to do two track one after another distribut it to left right channels each of them then you can have a very good stereo image... and even if u r not hapy with that..here one more zinger..first make two tracks seperate of the same riff or rhythm of guitars on a hi part then two on the low..and make the distribution in this manner
hi- 80% left and other on 80% right
lo- 30% left and other on 30% right
hope that you like the result...and one more thing there is a plugin called Canam Tools... its a good plugin to make the mono sound look stereo it gives a very good stereo image and also has an option of surround image i use it alot hope that you like it too...