Check the rock types in the vicinity. If the sample doesn’t match any of them, have a qualified geologist take a look. Though be careful of State appropriation schemes.
Magnet, magnet, magnet!
If one of those strong little shiny “rare earth” magnets doesn’t stick to it, it’s not a meteorite.
Also, if it is porous, or has gas holes like lava, then it isn’t a meteorite (and a magnet won’t stick.)
The exceptions to these simple rules (actually, just the magnet rule) are so rare that experienced meteorite finders never find a non-iron meteorite in their entire careers.