Some good info here.
I would add to this list something about image quality. All too often do I see this mistake on both sides of the fence. Websites are providing low quality images but on that same note Pinterest account owners (both personal and business) are making the error of pinning these low quality images. The rate of 'like' and 'repin' drops drastically when a poor image is shared.
The fix: Websites should host the best version of an image that they can find or make/take their own and any Pinterest user looking to maximize followers/repins/likes should stick to a quality standard.
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