The best advice I could give you is what many have already said. I found the main thing is to definitely use a punch to make a small dent and mark the center of your hole. This way the drill bit will not wander around and it will stay where you want to start your pilot hole. If you don't use a punch, nail, or something the bit will wander off target and your hole will not start exactly where you want it.
Drill your pilot hole with a small bit and then use a step bit, it will go through like butter and make the hole wider with no problem. Just remember to use oil, WD-40, or other lubricant and go slow and use a lot of pressure. If the metal gets hot and starts to smoke, stop and spray some water on it. Using to high an rpm will make the metal get hot very fast.
Go for it, have fun, and then grab a brew and marvel at your work!
John