Though there a numerous ways to identify a first edition and each publisher may have their own rules the following is a brief outline to help you get started.
Usually on the title page it will say “First Edition” or “First Published”
There may also be a number line like as follows. 10,9,8,7,6,5,4,3,2,1
With the last number 1 showing the first edition.
Now if your number line reads something like
10,9,8,7,6,5,4,3,2 this denotes a 1st edition 2nd printing.
A book club first edition is not a true first edition. There are a few exceptions but none that will be noted here.
When identifying a book club edition there are a few things that will show you immediately that the book is a book club.
There is no price on the dust jacket.
There are the words Book Club Edition on the dust jacket usually located on the lower inside flap.
Generally book club editions are smaller and weigh less than other books.
I would like to emphasize again that there are exceptions to the above rules and that they are only a general guideline.
Trying to determine first editions can be an exhaustive process. A reference set and bibliographies are used quite often.