There are several brands of pinking shears available. The one I am most familiar with are Gingher pinking shears. Sometimes it seems like you are spending quite a bit of money for a pair of scissors, but if you use them correctly, they should last you for many years.
I seem to have the best results when I cut through more than one layer of fabric at a time. This only works if the fabric is not too thick to start with. You also want to make sure and hold your shears in a straight line. If you are not used to working with them, it can be easy to work at an angle, but this is not the way you want to do it.
I also remember being told to never open and close the blades without having fabric between them. For some reason this will dull your blades more quickly. If you treat them with care, your investment should be something you will have for many years to come.