look at the bud structure... usually leafier is sativa, but it an also just be shitty cutting.

the calyxes (what would be a seed if it had been pollinated) are usually rounder and fatter on an indica, and skinny and pinty on sativa... Indica is very dense and skunky... Sativa is light fluffy and piney. but the only tru way to know is to ask the guy who grew it