My short two cents:

Buy a nice used bike that you feel comfortable riding. Ride.
Find a place to ride that works for you.
Find a good, customer oriented local bike shop. Visit them all and see what you think.
Get a comfortable saddle - you can use it on your next bike too.
Buy Joe Friel's book - "Cycling past 50"
Get a heart rate monitor so that you can gauge your effort.
Keep a regular biking schedule - weather permitting.