Required equipment:
1. DSLR or equivalent that has BULB mode.
2. Tripod (Duh)
3. Remote shutter cable
Step 1.
Switch your camera into BULB mode.
Step 2.
Enable Mirror Lockup (This will reduce camera shake)
Step 3.
Set your ISO to 100 and Fstop to f11-16.
Step 4.
Set your white balance
-Tungsten to Fluorescent range (3200K - 4000K) will give you dramatic blues and purples.
Step 5.
It might be hard to focus if you are not wide open due to obstructions so you could try and focus on something around 50 yards away, if you are wide open just use the infinity option on your lens.
Step 6.
Once you are all set up its time to take that shot. What you want to do is press and hold your shutter release (Different on different cameras) and as soon as you see the lightning strike release the shutter. Like I said pretty easy right, you might have to play around with this technique a bit but once you get it down you can try and include some foreground objects to make it a little more interesting.
Happy shooting.