What size wire should I use? Check this wire calculator: http://www.powerstream.com/Wire_Size.htm
What lights should I use? There is a great article hosted here that covers this question: http://jd.offroadtb.com/light_comparison.pdf
A full write-up can be found here in our forums: http://forums.offroadtb.com/viewtopic.php?f=27&t=8
David Ranton says:
The wire size calculator is a nice reference. As an electrician you can never have a wire oversized. (Unless it doesn’t fit in the terminal.) Bigger wire = Better