Some tips:
- Zip ties, cable ties, velcro ties, sleeves, clamps, basically anything that can hold two things together. Be creative.
- Try to run things parallel and perpendicular to one another for neatness.
- Put as much stuff as possible BEHIND the case.
- Take advantage of any nooks or crannies that you might find. Might need longer wire to compensate for routing.
Pics of half-completed build. Cleaned up cables some more after this:
Incidentially this is the first build which I'm satisfied with the wiring so far.
Case is Thermaltake Element G. Makes cable routing a snap (see 2nd picture). All that stuff is in the back; you just can't see it.
Having a high-quality PSU also helps. That thing at the bottom is a Seasonic X-560, with fully sleeved and modular everything. Definitely does help, if you don't want to sleeve cables yourself.