If you're using brickets, stop. If you're using lighter fluid, stop. Even if you don't do this crazy mod, buy a charcoal chimney and start using natural lump charcoal that pretty easy to find anymore. Lights quickly (with just one sheet of newspaper) and burns super hot. A bonus is that if you're just making a small meal it reduces the amount of charcoal you'll need to use by concentrating the heat.
Step 1: Needs
--An old Weber Smoky Joe grill (or equivalent)
--A charcoal chimney
--Metal cutting saw
--Welder (optional, but very nice to have)
Step 2: Getting To It
Turn the base of the grill upside down and put the charcoal chimney on it. Outline it with a marker.
Use a spring loaded punch to make the mark for drilling . . . using a punch gives the drill bit something to grab onto and work it's way in to the otherwise smooth metal.
USE EYE PROTECTION. The baked on coating (probably some sort of porcelain) will fly everywhere.
Once you've made your hole poke a metal blade through it and saw it out. Cut on the inside of the line you made because you'll want the joint tight. My friend Dean used a torch to cut his out.
Use a grinder of some sort to fine tune the size of the hole.