yeah, just go by the looks of the leaves. Indica will have Very fat dark green leaves while sativa will have very long & skinny finger leaves. The fact is that most all strains being circulated about & sold are hybrids of indica & sativa. Most of them having mostly indica genetics. For indoor grows indicas are used mostly. While sativas will usually have a better high they aren't grown much by ppl that are looking to selll or make money from their crop because indicas will produce more, stay shorter, & take less time to grow. So if you're in it to make money indicas are the thing. If someone is growing for a personal stash & wants the best high they can get without concern for how long it takes to grow or how much weight they get vs. how much electricity & work is put into it... well then a pure sativa would be the thing. & A breeders job is to try to combine the genetics & get the hi quality buzz of a good sativa combined w/ the short & compact, high producing & short flowering time nature of indicas. This is why most of your seed bank super strains will be indica/sativa hybrids (i.e. mostly indica, or mostly sativa).