Here is a little help on how to find that first edition:

The early Doubleday books all say "First Edition" explicitly on the copyright page -- there are other identifiers for these books as well (see each book-link). For books that contain strings of numbers to denote the printing, the important consideration is the presence of the numeral 1 in that string, regardless of the format of the numbers. Some possible variations of the printing numbers are:

1 2 3 4 5 6 7 8 9 10
1 3 5 7 9 10 8 6 4 2
10 9 8 7 6 5 4 3 2 1

All three of these denote a first edition. The numeral 1 will be removed for a second printing. Random House (Black House) is the exception to this. First edition copies will state "First Edition" on the copyright page and the number sequence will be "2 4 6 8 9 7 5 3".

Trim size is given because Book Club editions are often smaller than trade editions. Note also that Book Club edition dust jackets are occasionally found on first edition books to replace lost or damaged jackets. Book Club edition dust jackets are easily identified because they do not have a price marked inside the front cover. Later printing trade edition dust jackets will often have a different price imprinted on them from what is found on the detail- page on each book.
The table below lists the first edition covers for each of Stephen King's books.