if you're just learning to climb... DONT put anything on your legs, DONT wear boots! you will develop the squeezing muscle over time and it needs to get stronger with practice! it's like using a thighmaster. literally =)
when i have my students start climbing-- when you stand up and pull up and bring your body to the pole to stand, bend your left leg, have your foot pointing behind you, and bring JUST your left KNEE and thigh to the pole. don't put your left calf along the pole, don't do anything with that foot or calf. just have your left leg bent at the knee, and squeeze the bejesus out of hte pole with your knees/sides of your legs, right where your calf muscle starts and right next to your knee. get a feel for that-- how hard you have to squeeze-- first, and work up to standing without your hands. then you can put your left leg in position for a regular climb-- keeping that knee squeezing just as hard-- with the calf laid along the front of the pole, toes pointed.
a lot of times people rely on the skin of their calf, etc, to help them not slide down, when really the whole point in first learning the climb is to have your knees squeezing super hard to keep you up and do all the work for you. make sure the pole isn't between your thighs-- you have no squeezing power there, keep it between the sides of your knees and make sure you are really applying pressure with your right foot onto the pole too.
if you're a more curvy gal, you have more weight to hold up. also make sure your skin isn't DRY-- you'll slide right down-- moisturize the night before class and wash it off in the morning. good luck! you'll get it =)