Hi Laura!
You can book your Dining reservations online. To do so, click here to be taken to the Reservations page.
To determine which restaurants are covered under your plan, click here, which should open the Dining Plan for 2011. If you're interested in 2010, click here.
The Dining Plan itself will give you a list of restaurants on the plan, along with the park or resort it is located.
Character dining is handled the same way as normal, or non-character dining. When you get to the Reservations page, you'll be able to filter by character dining if you so choose...
Good Luck with all your reservations!