It's not an easy question to give a general answer to as what to look for will vary from one title to another. But no, it won't say 1st pressing anywhere on it. For a record to be a first pressing, it just means that it's the original issue so not a reissue and not a repressing, absolutely no changes to the record or packaging.
A reissue would be easy to spot as it would have a different catalogue number and often be on a different label as well. A repressing would be on the same label and have the same catalogue number but there would be telltale details that make it different to the first pressing. Those differences are what you have to check for. They can be very obvious, eg CBS changing from solid orange labels to sunburst labels. At the other extreme, they can be very slight such as a minor change to the label rim text for example.
A lot of the time you wouldn't even need to look at the matrix numbers to tell if something is a first pressing or not as there will be more obvious ways to tell. And then, in some cases, the matrices won't even have changed on a repressing - obviously the bigger seller that the record was, the more matrix changes you'll get and the faster they will happen. But if something sold fairly poorly but remained on catalogue for a long time, you could see major changes to the label design but no difference in the matrix numbers.
The devil is in the detail and, if you don't know, Discogs is a good enough place to start although, being a user edited database, it's not always right. But it will certainly give a general idea and be right in most cases. To be honest, 45cat is often better for detailed info on singles, especially ones that have had several pressings.
