1. Sleeve First press albums from an older era of vinyl record collecting will tend to have wear and tear far more than a record in a later batch.
2. Barcode If you can see a barcode on the sleeve, then you likely are not in possession of a first press.
3. Catalog Number You can very easily use a database like Discogs to find your own catalog number and see whether your record is indeed a first pressing.
4. Edition At this point, it can be of use to check the specific edition of the album.
5. Center Label The center label might even be marked a different way to signify that the pressing is indeed a first pressing of supposedly the best-sounding records.
6. Dead Wax Many of the large conglomerate record companies and manufacturers will use the same method, so it is certainly worth checking for the information.