Often times I find loot that has a small amount of durability lost. I tend to "repair all" as my first action when I visit the blacksmith, where I usually sell my stuff. So when I sell stuff, I'm selling it at full durability. Does this get me a higher selling price, or should I just sell it without repairing. Which option nets me more gold?
Originally, it was important to repair everything before selling it, because you'd make much more money that way.
However, this was later changed in patch 1.8. There's no benefit to repairing items before selling them in the current version.
From the 1.8 patch notes: "Items sold to stores are priced as if they were fully repaired."
Also note that hitting "repair all" does not repair items in your inventory: only the items you have equipped are repaired by the "repair all" button. So you don't have to avoid hitting "repair all" before selling your items either.