If you do ride him again, ask her politely for one. Ya know, "I don't think I can get him to go.. I'd like the extra encouragment incase I have trouble, it'd make me feel better" or something. :)
When you canter, keep your back arched and sit up. Don't post, lol. :).. I still have trouble with staying in my saddle so don't feel bad if your bouncing a little! (:
Make sure your sitting trot is good and you know how to sit without bouncing a lot before you start to canter.