It is usually easy to find one if this is the author's initial book tour. However, often first and second editions are mixed on the same display. One way to check this is by looking at the publication page, under the publishing house for the numbers, 10,9,8,7,6,5,4,3,2,1. If the numbers begin with 2 or the letters with B, it is not a first edition. As in all things, collect what you love, not what may bring you monetary wealth.
Nothing is guaranteed.
The trends and markets are constantly changing. It is also recommended that you have the book autographed to you and ask the author to include your name in the inscription. This helps authenticate the autograph and illustrates that it was not a mass produced signature. Another hint is take a camera, and ask someone to take your picture with the author. This also adds value to the collection, by demonstrating proof that this event did indeed occur and you were present.