Position your body
You want as much downward pressure on the balls of your feet as possible. Leaning too far into the wall may lead to sliding right down the rock. Keep your butt out and your hands in front of you. This style burns your calves but offers the best position.
Smear your feet
Use the friction between your shoes and the rock to hold you in place. Get as much weight onto your foot as possible. Look for tiny edges, ripples and other dimples in the rock. The smallest wrinkles can be an excellent place to smear your foot and make some upward progress."Trust the rubber because the rubber is way better than it was in the 70s," said master slab climber Hayden Kennedy.
Moving well on slab routes requires stepping up. Usually the moves aren't physically taxing but require intense balance. Place your foot on a hold and commit to the process, shifting your weight over and then onto your foot quickly. Slabs become easier when you move confidently. "For me it helps looking to your left and right and try to stand up as straight as possible," said El Cap free climber Lucho Rivera. "Always remember to stand on your feet and don't overgrip. Its easy to do on slabs. And relax if possible, tho sometimes thats a hard one."
"Be stoked to go for it even if you're going to fail." said Kennedy. Having confidence and a willingness to be a little bold helps tremoundsly with the difficult mental game of slab climbing. Also, Remember that slabs are way easier in the shade.
Wear Good Shoes
Stiffer shoes work much better on slabs. Make sure your soles are clean. Slab climbing requires strong feet and solid calves. After intense slab climbing, some climbers complain of sore feet. Stiff shoes help alleviate this problem and make standing on small edges easier. Check out a good pair of TC Pros for really tough slabs.
There's lots of great places to go get your slab climb on. Try the Dike Route (5.9) in Tuolumne, FreeBlast (5.11b) in Yosemite, or Initial Friction (v1) and Blue Suede Shoes (v5) in the Camp 4 boulders. There's amazing slab routes in Squamish as well. At Ironworks, there's a great slab in the back of the gym as well as a wall in the front.