Okay first, ALWAYS LIFT WITH YOUR LEGS, most people know that, im just verifying. Do not lift with your back you'll get hurt, and it's harder.
To be a good base, you need strength mainly in your legs, your arms, and abs.
If your not the strongest, lift weights, and stunt A LOT. Some open gyms have places where you can learn to base, or practice basing, go there. The more you practice the better. A very important part of being a good base is lots of strength. Lift weights and do lots of arm circles, push ups, handstands, etc, to build up arm strength. Also do crunches, v-ups, planks, anything to help your core. And try riding your bike, going on tread mills or anything like that to build up leg strength.
Also, if you are the kind of base who is always wobbly when basing, try balancing a paint can or a heavy soup can on your hands as if you are basing, it will help you. Just make sure if your using a paint can you do it outside for when it falls and breaks:)