I use kids scissors with the colored plastic handles. I'd make sure its a new pair though. You can buy plant specific trimming tools, but what's the point?
I use a pair of plant tissue scissors. 4 bucks @ Drs. Foster and Smith. They're nice because they have a small tip. Which is good for precise trimming of stem plants.
For many stem plants, you can simply pinch off where you want to trim unless you want to be more precise about it. For plants with a rhizome, a good pair of sharp tissue scissors or razor blade is a must.
The cleaner the cut the better. Less damage to the cambian tissue means faster heal time, and that energy can be put into growing new stems from the buds. Also it helps keep diseases out of the plant.