To find out if you have a drain, pull your Negative clamp off the battery and stick a test light in-between the Neg. post and Neg. clamp..
If it lights up you have a drain..

If you've caused it by your alt. wiring, that's an issue itself and check the 59StatoWgn's link..
http://www.trifive.com/forums/showthread.php?t=17260

Some newer accessories like radios etc have a weak constant drain to keep station memory intact but if it's a glovebox light, trunk light or other accessory drain, leave the test light beaming as above and pop fuses one by one until it goes out to help identify which it may be..

Good luck!