a lot of your 'riding style' will be connected to what you have been taught so far, eg saddleseat. Prepare for some learning curve :)
For gripping with the lower leg, I find it helpful to chant in your head (or out loud if you don't mind the funny looks, lol) "hug the horse, hug the horse". That is essentially what you want to be doing, gently hugging the horse with your legs. You don't want a tight grip with the lower leg, as that will, in my experience, push you out of the saddle more, as well as may confuse your horse - leg means go, or go faster.
As for cantering, it very well could have been the smooth gaited horse canter you are used to, and now a normal canter seems rather 'ejectable', lol. Learn to move with the horse's movement, without pumping your hips every stride. You'll get the hang of it!
Your foot sliding forward in the stirrup tells me you are not sinking your weight into your heels. My instructors used to tell me to pretend I had a heavy weight pulling my heel down, and that helped a lot. Don't push your toes up, sink your heels down. Pushing toes up will just make your leg get out of position. 'hugging with the lower leg' will help this too, IMO.
Glad to hear your first ride went well, minus the heat induced dizziness.
Last edited by EdmontonHorseGal; 07-16-2013 at 08:02 PM.