I like to think heavy. Weight in your seat. Really sit. Rest your feet in the stirrups, but don't be tempted to stand. Gently support your legs against the horse. Grip a bit, but don't squeeze unless you're cuing. If you feel comfortable neck reining or just letting your horse "cruise," try holding on to the cantle of the saddle to help yourself sit. Don't try to hang onto the saddle horn, it will pull you forward.
A stubborn horse walks behind you, an impatient one in front of you, but a noble companion walks beside you ~ Unknown