There is no sure fire way to confirm a meteorite by external observation and non-destructive testing. Even things claimed to have been observed falling often turn out to be terrestrial stones dropping from the undercarriage of aircraft or being thrown large distances by trucks travelling at high speed.
There are a number of ways to confirm that an item is not a meteorite, but nothing which works conclusively the other way round. The best you can do is look for features which are potentially diagnostic as a way of narrowing down specimens which justify further (expert) testing.
‘Windowing’ to get a view of the interior is an additional useful way of gathering more information. That can again tell you if there are features which rule out a meteorite, or help you narrow down promising specimens… but you need to know what you are looking for and what you are looking at. Most people don’t have that kind of knowledge but, at a simple level, it’s not a meteorite if:
- It’s obviously metallic or has metallic flecks but is not strongly attracted to a magnet.
- It has exterior vesicles as anything other than small and part of a thin glassy fusion crust.
- It has interior vesicles in significant numbers or of significant size.
- It contains visible quartz crystals or other sizeable crystals which aren’t yellowish/greenish.
