how to tell on first pressing vinyl releases


I started some flea market and ebay searches and am perplexed on how to tell if an album is a first pressing release or a later release.

Also are less than 180 gram re-releases decent quality (think jazz reissues in the $10-15 range from Acoustic Sounds)

I did luck out on a two eye Brubeck Time Out and what appear to be first issue Jose Feliciano and Joni Mitchell discs.

thanks
Tom
128x128audiotomb
Thanks for all your answers.

The info stamped in the dead wax is the same on both LPs that's why I'm extra perplexed. But the thickness of records as mentioned by Mmakshak is interesting to me because one of the vinyls I'm talking about is thicker than the other, has a different feel and is heavier. It's almost like a 78rpm grammophone record!
Any more info you might have is more than welcome. Does anyone know if labels from any particular period were laminated?