Make sure to utilize the Emerald club program! You can pick your own car out upon arrival from the Emerald aisle. Much smoother process than the "other" guys.
Every year they have a promo called one two free which is a great way to earn free days on top of the normal earning program. Be sure to check it out. Typically runs August-February
Make sure you check for your belongings before you drop off car. I accidentally left my phone in car when I returned it to Midway-didn't leave building- tried but wasn't able to reclaim it. Watch Out!
Get last minute deals on car rental rates for business and vacation travel at Midway Airport with National Car Rental - Bypass the Counter at the airport with the Emerald Club.