Growing up in the North (Alaska), I've used axes and hatchets for decades but I'm pretty new to machetes myself. Now I live in the hot South (Texas) and I've been using a machete almost daily for the last week clearing some thick brush from the back of my property. I've found that the technique with the machete is much different than with an ax. Whereas you'd let the weight of the ax drive the stroke into the wood, with the machete, it seems you're really slicing the material more than chopping it. I find that drawing the blade across the branches, vines (whatever the vegetation is) as you strike makes a much more effective stroke. With the ax, you really aim to make the beard contact the material with velocity and weight to give you a solid chop--almost aiming to just bring a single point on the ax bit onto the wood (concentrating the energy to one spot). The machete lacks the weight of the ax. What the machete blade lacks in weight, it makes up for in length. Basically, I find that by slicing (letting more of the length of the blade contact the material as I draw it across), I get much better results on grasses, brush, and light weight vegetation--than if I were to use the machete to "chop" the vegetation down. In spite of all the YouTube videos of clowns showing themselves chopping wood with a machete, it's better used much more like a sword than an ax. If space permits, I find long, sweeping, slicing strokes with power (I put my back and hips into it) make the machete SUPER efficient at clearing swaths through the brush. Using this technique, I've lopped off 4 or 5 1" thick azalea (a surprisingly dense wood for it's size) branches with a single stroke.
As far as safety rules, depending on what you're cutting I'd recommend wearing safety glasses. I've found that with thick, stiff brush sometimes the branches that you didn't remove will spring back and take their revenge on your face. Also, make sure that the handle grip fits your hand well enough to prevent the machete from twisting in your hand. If it twists, not only will your stroke be ineffective--or may be deflected entirely by the branches you hit--but you can also hurt your wrist.