Okay well I have been lurking around but have not contributed, so I figured I would do a mini how to, and what to know for HID's or Xenon Lamp systems, relays, Kelvin ratings and so forth. Hope this helps.
Okay, here is my car, it may not be your taste but it's clean cut and I like it.
Okay so lets get into it, there's two options. 1. OEM. 2. Plug and play kits.
When looking for HID's there are things to concider.
1. Color or "Kelvin"- Simply put the higher the kelvin the less out put. So 3000 Kelvin used in most fogs have the best output.
2. Lumens- This is the measure of usable light, the more color like blue which strains the eyes, or purple, the less lumens. Anything over 8000k has less lumens than Hologen Bulbs.
3. Projectors- These are optics used to project (Hence the name) the light in an equal pattern on the Road. Reflectors are what all J's come stock with, these will scatter your HID's and look horrible and WILL oncoming blind drivers.
The color band is often what fools people into getting Blue, or 8000Kelvin pr above kits. The color band is a result of the optics and will make the cars OEM lights color shift from white, blue, yellow, purple, ect. while they approach you. This is my guess on where the colored kits got there routes.
Now Let's start with my Fog Lights. They are Blazer Brand Projectors with a 6000K kit, they accept stock 440(I might be off on the light numbers) foglight bulbs if you want to stick with halogen then you can put your stock bulbs right into these projectors.
Here is a picture with just the fogs on and DRL's disabled to preserve the bulb life (See DRL sticky for info on dissabling them). Notice the razor sharp cut off, to not blind traffic, and ofcourse the blue, purple, ect. color band that gives me that classy color flicker, but great white, and usable light on the assphault where it counts, and these are just the fogs alone.
Here is a wall shot
Here is down an alley
Now since Retroing is expensive, I opted to simply Bend the sheilds in my ebay projectors. The mod is just slightly bending them until you achieve less glare and a nice straight or sloped cutoff. They will work just fine. OEM is better, but again if you don't have alot of money theny ou do the best you can right? Right, Moving on.
Here is a headshot of my setup (also ignore the blue Highbeam buld, it has not been used since my HID's went in lol)
Now that we have that covered,
ALL KITS!! I mean every kit you will need a relay harness, to aquire one you can make one or just type in "HID RELAY HARNESS" one ebay. These are manditory to preserve stock wiring and not fry anything.
Here is a picture of a kit with Hella projectors wired to a relay, the wires towards the rear are the power and ground.
Here is a simple H3 size bulb comparison to show how kit or rebased bulbs can have screwed up focal points, hence why throwing these in a stock lamp blinds drivers.
Well that is really all, since it is late and this should be enough for you to have a fair understanding, and I won't spoon feed you info. HIDplanet forums are also incredibly knowledgable people for help as well.
Be safe, and remeber, yes you bright lights might be blingin' YO, but there could be children or elderly in other cars. Do you want put them in danger to have blue headlights? Be responcible and always keep other drivers in mind.. not how blue your lights can get.
Hope this was a bit of help to people and answered some questions.
Later,
Cavy610
" Aint nothin' but a Peanut!"
headlights not so much 
if they look bad on the cav i might do a retro on my pos truck
