The first consideration of ladder safety is, “Can the job be done safely with a ladder?” If the answer is "no," find another way to do the job or have a professional do it.
For example, if you need to trim tree limbs where there is no stable place to support the ladder or where the branches are likely to fall on the ladder, try to find another method. Could the trimming be done more safely with a pruning saw on a pole or with a rented scissors lift? If not, it might be time to hire a professional. Professional help could be cheaper and a lot less painful than a fall.
Serious falls are common; every year about 300 deaths and 175,000 serious injuries from falls occur in the United States.
General guidelines for portable ladders
Not all jobs can be done safely with a ladder or by one person with a ladder. If the job can be done safely with a ladder, there are several basic considerations in doing it safely, whether the ladder is a stepladder or an extension ladder.
Read and follow the instructions for the ladder and for the tools you are using.
Be sure the ladder is strong enough to support you and the material and tools you are using. This means that not only should the load capacity be sufficient to support the combined weight of user and materials, the ladder should be in good shape. The ladder should have a label showing its load capacity. The four common classifications are
Be sure the ladder is tall enough. When you're on a stepladder, you can reach 2 to 4 feet higher than the height of a stepladder. A 10-foot stepladder, for example, should allow you to reach a height of 12 to 14 feet. An extension ladder, however, must be taller than the height you want to reach. An extension ladder up to 32 feet should be at least 7 feet taller than the working height, a 36-foot ladder should be 8 feet taller and a 40-foot ladder should be 9 feet taller.
Make sure there's enough room for the ladder. A stepladder should have enough room to open fully; an extension ladder should have enough room to be placed at the correct angle.