Go to school, study, study, study, examine thousands of examples in museums and become an expert. Sorry, there is no other way. Most, perhaps well over 90% of meso and south American pottery pieces that come on the market are fake, they are things to stay away from unless you are an expert. The indigenous people of central and south America have been faking pottery items at least since the 1950s so most of what we see for sale in this country are fakes. Japanese sword collectors have a saying that out of every ten Japanese swords for sale eleven are fakes, it is a similar situation with pottery artifacts from below our border. A lot of pottery artifacts from the mideast and asia are now being faked too, dog eat dog world out there and faking pottery is a simple task. On my first trip to Mexico around 1962 I saw lots of people standing along roadsides selling terracotta objects that were "muy antigua" and all fake. I was lucky enough to get to dig around a bit back then and did find lots of original sherds, obsidian blanks for making blades, and some other cool things. One cannot go there and do this anymore.