If you don't know the breeding there is really no way to know. However if you are looking at a group of definite "possible hets" an experienced eye can probably pick out some good candidates.

Het Pieds sometimes have belly markers.




Het Clowns are usually brighter with a lot of white highlighting there pattern.




Here is my 66% Poss Het Caramel Albino. I feel she has a really good chance of being het due to her coloration (clear colors with white outlines and good contrast) and light head spot.





Hope this helps and happy hunting!