- memorize the time signature & the key
- count the # of bars in each section & the # of bars in each chorus - note the 'form'
- look at the chords to decide if the key is the indicated major or relative minor
- scan the chart to find chord changes for which you have bass lines to use
- scan the B section, interlude, chorus, etc., chord changes in case there are surprises
- scan for key changes, moving tone centers, slash chords & unfamiliar chord changes
- look for repeat signs, coda's, section marks, unison or obligato rhythms
If you are just beginning to play jazz, look at;
http://www.aebersold.com/Merchant2/merchant.mvc
Buying a book or 2 (actually Volumes 1, 2 & 3 with play-along CDs) will get you started a lot faster than trying to invent it on your own.
Good luck