The best credentials come through the American College of Sports Medicine (ACSM). If you're dealing with an ACSM-certified person, you can be relatively certain that you're getting up-to-date and accurate information.
The National Strength and Conditioning Association also has a number of levels of certification and people certified by this organization will help you to work in a safe way so that you don't get hurt.
How important is proper equipment?
Not getting the proper equipment or not wearing the proper shoes or clothes is another very common error. For example, many people have bicycle ergometers, or stationary bikes. Some of the less expensive models cannot be adjusted properly so the leg is not in full extension during the down cycle of pedaling, which can lead to knee problems.
And many individuals who start, for instance, a walking program, will have read that all they need is a comfortable pair of shoes. But they need a good pair of walking shoes with the correct arch and heel support and toe box. Once you start walking long distances, increasing your speed, and walking more often, if you don't have the proper shoes, you actually can get injured in what is probably the safest form of exercise.
