Go to;
http://lighting.mbz.org/
for the right bulbs. I'm using 100/130 German bulbs. They are the real high watt bulbs and *not* the Super Lazer Ultra Blue White colored crap that people use for the cool LOOK but are really sub par performers (and way expensive). These 130s light up the night, unbelievably bright. Burns the paint right off the Tuner Boy who's in your way!
You should install the relays as Noah mentions. I've used a number of the ones from Marcus Sucro
http://members.rennlist.com/msucro1/relaykit.htm
$20 and 20 minutes and you've protected your dimmer/directional switch from frying and also made all kinds of current availlable to the headlights so they work right and last. My bulbs have been burning bright for 1 1/2 years and 20K miles, and I run low beams in the daytime. Don't go with big bulbs without the relays.
The quartz halogen directional, brake, and running lights will also save one's ass from other bonehead drivers. They are BRIGHT. Recommended.
Jens