First off, kudos to you for working with rescue horses. But the first thing you want to know is that you are safely handling these animals who can seriously hurt you. (your safety, that is.) What I have learned about horse people is that they are "all right, all the time," and seldom agree with another horse person. That said, use your intuition and common sense as your guide, and seek out a helpful coworker at the rescue, or someone where you are taking lessons who you think is doing things the right way.
There are many opinions out there, and it is indeed difficult to weed through all of them. Once you get to know the horses a little more you will get a feel for their individual needs, and develop an appreciation for their unique personalities. Regardless of anyone's amount of experience handling horses, there are some things you just can't do with some of them that you can with others. Above all, RESPECT is key- they need to see you as higher in the pecking order, and this can be accomplished with confident body language and an even, calm tone. In my opinion (see? what did I tell ya?) heavy hands and rough approaches are not your friends. Always ask first, then amp up the pressure if need be.