Just remember that when two up, you'll need to put more input through the steering.
When I'm riding solo, most of the turns are initiated by my feet, when I'm riding 2-up, handlebars do most of the work.
Also, don't forget to adjust rear pre-load for taking pillions.
Arrange a system for stops and turns etc. For example, she hits your shoulder to say "turn here" and digs you in the ribs to say "stop you fool, I need a pee and I don't think you want a wet back!"
Slow speed turning will be the biggest difference, but when you're up to speed, it's almost like the pillion's not there (don't forget to check periodically, or she might get a little sore about being left at a service station etc).
