Hello there!
I will also add that it varies from drummer to drummer. Some drummers prefer a lot of tone and resonance, thusly leaving the reso. head untouched/uncut. In all honesty though, it really is about how much
attack and definition you want your bass drum to have. The bigger the hole, the less resonance and the more
attack you'll get from your bass drum. Right now, I have an uncut reso. head, but I'm considering installing a small 4" port hole for micing purposes and to get just a little extra definition to my sound.
As for installing the holes yourself, I wouldn't recommend trying to freehand it. Check out musiciansfriend.com in the sticks/heads/accessories section; they usually have stuff from
Remo or
Aquarian, etc. They make templates that are basically round stickers; you stick it on the front head wherever you feel like it should be and then you cut the inside of it out with an exacto knife or something like it. Make sure to take the head off of the bass drum when you do this. I watched a friend try to install a port hole while there was still tension on the head once: although the end result was really funny to watch, there is still a tapestry of obscenity hanging somewhere in the mix of space and ozone over Lander, WY as a direct result, and the new head was pretty expensive.
I hope this helps.