I just got an old Schwinn. What should I do to make it rideable again? Also, how can I identify the year and model?

To make the bike rideable again, replace:
tires
tubes
cables
brake pads

Clean and regrease the bearings in:

Front Hub

Rear Hub:
Bendix

Sturmey-Archer
Model AW
Model S3C
Model S3C Bulletin A
Model S3C Bulletin B
Mark IV

Derailleur
Quick Release Rear Hub

Headset

Bottom Bracket

Lay the bike on its side, and drip some oil into the freewheel. This is all it needs. Oil the pedal bearings.

Clean and oil the chain, shifters, and derailleurs.

Have the wheels trued if needed.

Online bike repair:

http://www.parktool.com/repair/

Kickstand removal and other tips by Mark Smith:
http://www.bunchobikes.com/repairindex.htm

You can buy used parts on
http://www.ebay.com

Paint for 1940's - 1950's Schwinns:
http://www.restoreclassicbicycles.com/classics/paint/paint%20set%20intro.html

Paint for 60's – 70's Schwinns:
http://www.hyper-formance.com/paints.htm

How to find the serial number, year, and model:
http://www.trfindley.com/pg_schwinn_cats.htm

How to ship a bike:
http://www.trfindley.com/pg_bike_ship.html