Be honest how many hours have you spent on Pinterest repinning items from other pinners' boards to yours. We all do it ~ heck that's the reason behind Pinterest, sharing ideas. Two points here:
1. Be sure that anyone who views your pin will be directed back to the original site. You are able to correct any url errors or misdirection on the "edit your pin" page using the link area.
2. If you repin from someone else's board be kind and "like" their pin. It is a simple way of saying "thanks for finding this great idea!"
It isn't always easy to comment on a pin if it is a recipe or something we plan on using/trying in the future. Every now and then we'll stumble across a pin that we're familiar with. Sharing your experience both positive and negative is very helpful not only to the pinner but anyone who views that pin in the future. For instance the other day i was looking for a afghan patter and found a pin that was described as the easiest afghan for beginners. After spending a few minutes on the site I returned to the pin to comment how many experienced crocheters had found the pattern difficult.
Real Life Experience
If anyone out there has done/achieved all that they have pinned on their boards then this isn't for you. The rest of us however I believe I can say with definite confidence pin more than we'll ever "do". I have 2 different thoughts on this
1. Be sure to go back to your original pin and comment your result
2. Create a board for those pins you have actually done. My board is called Real Life Pins. This is great to post the pictures of your results. Sometimes it is really nice to know that not everyone can create projects that look like they were done by Martha Stewart.
Thanking Original Source
Many bloggers as well as commercial sites now have Pin It buttons on their pages which let them know when someone has shared their content. For those times when I pin something from an original source that doesn't have a repin button I take a moment and let the blogger know I've shared their info. More than once I've gotten a thank you as well as finding out they visited my boards and/or my blog.
So there you go my input on being a considerate, upstanding pinner :)
As always feel free to visit my boards on pinterest.