Like any other social media, you have to be an active participant and pin a variety of things to a variety of boards, do a lot of re-pinning, sharing, and commenting for the best results.
On your pins, share a bit what they are about, but don't give everything away. An example might be "Only 3 ingredients and it's really delicious, you should try this recipe"..
I have boards that are search engine friendly for their titles also. For example, my Halloween board did very well because it has a simple title "Halloween the best Holiday" instead of "spooky stuff" etc.
Pinterest boards do come up in search quite a bit - so have a few boards that you really make special and make sure they have search friendly names. My Halloween board has over 1,000 pins from all over the place, including just a few from my own material. When possible, I don't just repin - I'll add to the text or change up the comment a bit.
Also, participate in Pinterest groups where you can. That collaboration helps a lot if you get on a good active board.