I did this on my CRX a few weeks back... My suggestion, is first get the measurements for your car, and the lights u plan on installing (some may be bigger or smaller)... A dremel tool is a MUST, if u dont have one, or something similar, buy one, or take it somewhere to get it done! Now make a template using a ruler, a pen (or marker), and the measurements of your lights...

Next, using the measurements for your car (where to place the light exactly on your fender), measure horizontal to where it should go, now use masking tape and tape that line, then do the same for verticle line... So now u have a L in your fender, and place your template perfectly in the corner and tape all around it... Measure again, make sure its perfect, or damn close... Measure twice cut once! And then when your happy, start cutting...

How I cut mine was, I cut out a rectangle first, and then cut the notch out on the side, its much easier doing it like that, then trying to cut all around it...

Cut like this (hope this comes out alright..hehe):

--------------- <first cut on top of rectangle


--------------- <second on bottom of rectangle

then to the verticle:

| |
|(3rd cut) | (4th cut up/down)
| |


So now u have a rectangle:

_______________
| |
| |
|______________|

Now cut the notch:

....__________ (this was your first cut on the rectangle)
...|
-- <5th cut (on notch)

-- <6th cut (on notch)
|__________ (this was your second cut on the rectangle)


So now you should have a similar shape like this:

....._______________
....| |
..{ <notch here |
....|______________|

Now test fit the side light, and if it dosnt fit, keep cutting carefully till it fits...

Damn, it didnt come out right... Ill try and make a diagram in photoshop what I mean later... Been meaning to do that...