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.