Pinterest Pet Peeve #1: Not changing the caption!
Okay, so if the pin goes to a recipe for banana bread and the caption says "banana bread recipe," you obviously don't need to change the caption if you don't want to. But if the pin is a picture of a kitchen and the caption says "our kitchen cabinet remodel" and you pinned it because you like the light fixtures, change the caption! It will benefit you to change it so that you remember why you pinned it and you can actually make use of it!
As another example, I have some of my photography on Pinterest, including photos of my daughter that have captions like, "My sweet baby girl!" I'm flattered if you like my photos and want to repin them, but please change the caption as it pertains to you and how it inspires you, or why you repinned it. Last time I checked, I was the only one in labor with her for 2 whole days, so "my sweet baby girl!" doesn't really apply to you! ;)
Pinterest Pet Peeve #2: Not linking a pin to its original source.
Always give credit where credit is due. This applies to Pinterest, too. If you are the original pinner, pin to the original source. And if it is in a blog post, pin to the actual post and not the blog so you (and other pinners) don't have to search the whole blog to find what you pinned.
If you are repinning, check that the pin goes where it should. I know, it doesn't always. And sometimes you don't have a lot of time and pin it just because you don't want to lose it. But try to go back and do a little research when you have time. Try to find the original source. It will help someone else find where they can buy it/get the tutorial/learn how to do it etc. and also give the appropriate credit to the creator.
Did you know that using Google you can search by image instead of text?! It is amazing! Go to Google. Click Images. Click the camera icon in the search bar. Then search by the image you're looking for. It is, surprisingly, really accurate! And it often helps me find an original source. I use this to pin directly from the original source and then go back and delete the one I repinned that went somewhere else.
Okay, I'm off my soapbox now. Go on! Get pinning and use Pinterest to its full potential! Give credit where credit is due! And while you're at it, come find me! :)