When you notice the first signs of a shed bump the humidity up. Also during the shed having moist moss (or whatever you use) in all hides will help make sure it has a good shed. The most important part is noticing the signs of a coming shed quickly. Its hard to catch up on needed humidity.

Doesn't sound like your shed was bad. If your snake is new to you it may not have been in the proper humidity before and with you providing the proper environment it will do fine in the future.