I suggest that you read this for wiring information.
With regard to your question about CAT6 and mains cables, the big thing to remember is that if at all possible you should avoid a situation in which a CAT6 cable crosses a mains cable, or vice versa. If crossing is unavoidable it should be at right-angles, thus minimising the contact or proximity point.
Otherwise, try to keep a degree of separation between mains cables and CAT6 that run parallel - how much separation you can achieve will depend on circumstances. Keep the radius as slow as possible when CAT6 cables turn corners of course, and avoid kinks like the plague.