OK, i work in retail and never once missed a fake note. I dont check with UV or the watermark. Well, i've never had to anyways. As your counting if you count by rubbing your finger over the middle section you'll actually notice that the ink is raised off the note and provides a rougher feel. That's very hard to replicate, especially with a photocopier. If your a bit iffy look at the clear window and it should have the demonation raised on BOTH sides and not just one.
Also, dont trust the UV test, there are a lot of older notes out there that the UV ink has rubbed off and wont show the denomination (there is the denomination on $20 and up notes just above the clear window that reacts to UV) and sometimes the ink on the serial numbers rubs off too.
Another thing is the 7 pointed star, when you look through the note you should see all 7 points, but when looking just at it without a light behind it you should see 4 or 3 points (depending on which side).
If you really want to get picky also hold a magnifying glass over the ink i was talking about and it's not just ink, it's actually micro printing of the denomination in words. Eg. a whole bunch of words saying FIFTY DOLLARS and not just ink. Most devices arn't good enough to catch the microprinting and reprodice it, if they are then hell, they deserve to use that note.
