One of the first things you should know about English riding, is that is is automatically completely different than Western riding. Your stirrups will be shorter, right at your ankle bone (for jumping stirrups), the saddle will be a different shape (and there are different English saddles for different English disciplines). The saddle is smaller and made for more contact with your horse and your seat. You want your heels down (not too far that your weight is shifted into your heels, but not too little that your weight is still in your toes). The stirrups should lay on the balls of your feet and also your toes should be pointed inward. Something that riders (and I) struggle with when transitioning from Western to English is that your toes have a tendancy to point outwards into what my instructor calls "Duck Feet." Another thing you should know is that your posture should be very nice, but you still need to have a soft back and body and let your hips move with the horse very nicely. Also having soft hands and quiet legs makes a huge difference in your riding. Make sure your legs are quiet (they aren't moving a lot) and it will improve the look of your riding greatly.
If you have any other beginning English riding questions, feel free to message me:)
Hope this helped,
Patience is the best. Don't get frustrated with the horse. Make sure you can make a straight line through your body from your head to shoulders, elbows and toes. It's also important to keep and contact with the reins so that when your riding they aren't bouncing and going everywhere
Find a good trainer to start with. Breaking bad habits is more work. Keep your eyes up, heels down. If your havng trouble posting, bring your lower leg back until you can rise out of your seat almost effortlessly. Id love to give you some pointers if youd like to send me a video through instagram and i can give you some pointers and tips. Id love to help
Eyes up and heels down! If working on the flat keep a deep seat and if over fences keep a light seat over the jumps(with a nice solid 2-point) and a deeper seat right before the jump. (this can't sometimes change depending on your horse) When sitting the trot absorb the shock with the back on your thighs and keep your back straight.