It's better to look up than down. Down = you're going down, girly.
Try not to squeeze. A horse is like a bar of soap. Using leg properly is fine but pinching with your knees, heels, or thighs = you're going to have a bumpy ride. It's counter intuitive but relaxing is the best way to go about it.
Either way you definitely should take note of any bucking.
But sometimes bucking is a physical sign, so when your horse bucks it's good to get them looked over and checked out for any signs of pain. Other times it's a training issue. Either they aren't ready or they are too excited or just don't want to a person on period.
"Strength is the ability to use a muscle without tension"