Here is a good link-
http://foolandhismoney.blogspot.com/...ath-taxes.html
The 24 hour thing appears to be wrong. Personally, I define a session as each time I sit down and play. If I get up and go get lunch or take a nap and come back, that is a new session
Granted, this is probably all meaningless as the IRS is most likely not going to be hunting small-time poker players down, but better safe than sorry.