If you just bought your first jazz Real Book, or you are thinking about it, , you're likely looking at the "The Real Book" Volume 1. There are many different "real books" out there now, but this one is a enough place to start as any. But once you get home you probably looked through it and wondered where the heck to start. It's a lot of songs, some more challenging than others.
The Real Books are great for many reasons, though they have their downsides. One downside is that they contain a lot of songs that people don't really play anymore. For example, how many times have I ever heard anyone play "Peaches En Regalia" by Frank Zappa? Never.
Also, just because it's volume 1 doesn't mean it's the easy stuff. It's only called Volume One because it's the first collection they made.
If you're in this boat, here is a short list of songs from this book that are good places to start because 1) they are fairly easy, 2) they contain fewer chord changes and require fewer scale changes for soloing, and 3) they are more familiar songs to many.
Autumn in New York
Don't Get Around Much Anymore
Easy to Love
Freddie the Freeloader
Green Dolphin Street
I Could Write a Book
I Got it Bad
Some extra advice: Start by listening to the songs first. Just go to YouTube and type in the name of the song and listen to a few versions. Being familiar with the songs will help you immensely.
Once you have the melody stuck in your head, start by reading through chords, measure-by-measure, interpreting the chord symbols carefully.
Try playing the melody, slowly at first.
Once you have it up to speed, use a jam track from Aebersold, or search Youtube for the title of the song plus the words "jam track" or "backing track" and try playing the chords or melody along with it.
Analyze the chord structure and determine which scales you will need to solo over the song.
Good luck. Have fun!