I've never really trusted the bubble levels in the games, I use this product...
http://www.amazon.com/AccuRemote-Digital-Electronic-Magnetic-Protractor/dp/B006JR8XBG/ref=sr_1_1
and it works real well to get a quick and accurate reading on the angle of the table. There are others out there I'm sure, but this one is built with quality and magnetic so I if fits for other uses too (I have to sometimes measure elevation and declination angles of old school satellite dishes in my job which are far more specific than a pin needs to be).