When riding a half pass, you always want to feel like you are riding straight to the short end with your seat. Look at the short end and just position for the half pass but keep riding straight to that short side!!
You always want to feel like your riding both sides of the horse! Don't focus on one side!
When you get in the saddle look down in front of your saddle and imagine a box that includes the front of your saddle, the withers, even with your hips (width wide and height). This is what I call "home base" for your hands to live in while riding. If you picture that box its easier to know where you should have your hands without someone telling you.
Always look where you are wanting to go, have a plan so that your horse clearly understands where he/she is supposed to go!
Make sure when you give an aid you know WHY you are giving that aid! If you don't know, how is your horse supposed to? When I use my leg, i know if I'm asking for sideways, more ground cover, or more lifting of the shoulders.
Always ride in a good balance, it starts with your position before the horse can be in balance. You should feel like your leg is long, you are even in the saddle (no collapsing) and upper body tall shoulders over your hips.
If I pulled the horse out from under you you would land on your feet!? If your not in balance, how can your horse be?