I set up a simple training plan on a spreadsheet like these.
http://marylandlung.org/x2/file/e00d...8af0923de0.pdf

Other good info is all over the ‘net.
http://www.auburncentury.com/training.html
http://www.teamestrogen.com/articles/asa_century.asp
http://www.ultracycling.com/training/century.html
http://www.active.com/story.cfm?stor...tury_challenge
http://www.geocities.com/ne_century_rides/training.html

Some people use gel. Others use energy bars like Clif and Luna bars. Cytomax, Gatorade or Endurolytes pills for electrolyte replacement. Others prefer regular food and pack a good old PBJ sammich. Use this training time to get you eating and drinking figured out because it is definitely one of the challenges. MP's comment about sugar spikes with gels is important to know. I am very sensitive to sugar spikes and once I eat a gel have to commit to start eating something every 20 mins or have a sugar crash.

Mix up your training plan with flat and hilly terrain. Vary your intensity. If your goal century is a flat ride, train your butt with lots of long flat miles. If it is a hilly century, train your legs with longer hill climbs on your long ride days.