Stay Close to the Wall
Many beginning climbers approach the wall straight-on as if they were climbing a ladder. While this may work for some lower-graded routes, greater technique is required for more difficult climbs. Watch seasoned climbers at the gym: you'll notice that they turn their hips into the wall, often shifting from one side to the other as they move upward. Keeping your hips turned in helps keep your center of gravity towards the wall. If you pull your hips or your bottom away from the wall to raise your foot, you pull your weight away from the wall, which could cause you to fall. Also, try moving your arms up in a sweeping motion away from your body. Moving your arms straight up in front of your torso can create space between your body and the wall, which can also throw you off balance.
Extend Your Reach
Turning your hips into the wall can also give you more reach. If you're facing the wall and aiming for a hold that is slightly out of reach, turning the side of your body into the wall can give you that little extra length that you need. Make sure that you are reaching with the same side of your body that is turned into the wall.
Use the Edges of Your Feet
As you climb, pay attention to your foot placement. Try to use just the edge of your foot on the holds. As you begin climbing more difficult routes, you'll notice that some of the foot holds are too small to step on squarely with the middle of your foot. Climbing shoes are designed to make it easy to balance on the edges of your feet. As you move up the wall, you will use both the inner and outer edges of your toebox.
Use Your Legs for Power
Many beginning climbers will try to pull themselves up to the next hold with their arms. If you're new to climbing, you may notice that your arms wear out faster than anything else on your body, except maybe your hands. All of your power should come from your legs. Always place your foot securely and then push up with your legs, while using your arms mainly for balance. With prolonged climbing you will build your upper-body strength, but don't rely on your arms for upward mobility.
Keep Your Arms Straight
If you are climbing on any sort of an overhang, try to keep your arms straight as much as possible. This may feel awkward, especially if you are keeping your hips close to the wall: you'll find that your lower body is close to the wall but your upper body may be leaning back. This will help conserve your arm strength. Using your arms to hold yourself into the wall will wear your arms out quickly.