hi raz.
basically for holes, you need lots. some of the hobo stove designs are based round cutting the whole of the bottom of the can off, then you stand the can off the floor to maximise air flow.
if you're keeping the bottom of the can in, you'll also need a grate.
for dog food tin stoves you can use the cut out lid. clamp it to a piece of scrap wood or something, and drill in as many holes as you can. you really don't want a sharp tin lid spinning round your drill bit whilst you're trying to hold it. :shock:
the other source of great grates is recyling the grill out of a disposable BBQ, just cut yourself a circle about the same size as you tin with a pair of pliers.
raise the grate off the bottom of the can by sticking three small screws though the side of the can. just drop the grate in so it rests (at least nearly) flat on the screws.
if you have a hole saw it's worth making one of the holes in the bottom of the can relatively big. then you can blow into the bottom of your fire to perk it up, or stuff burning tinder in.
have fun,
cheers, and.