Well that's the thing about hets -- you can't tell just by looking at them. You have to know the history (parentage) of the animal, which generally means getting them from a reputable breeder, because it's very rare for pet stores to have much of a clue where their stock came from. Without knowing the parentage of the animal, all you could do would be to try breeding your animal to either a known het of the trait in question (albino, blizzard, patternless... whatever), or to an animal that actually displays the trait. If you end up with some babies that show the trait, then you've got a het

If not, then you probably don't (although even when you breed a het to an animal displaying the trait, sometimes it will take several clutches before you'll get a baby that shows the trait too -- it's all in the odds

).
Hope that helped a bit, and didn't just confuse you more -- LOL
Jen