I'd suggest 2 things:
1. Get a blacksmith, fletching, or carpentry repair deed (depends on what kind of weapon you are repairing) and use that on the weapon first.
2. Get yourself some powder of fortification. Each use of the powder will add 10 durability to the weapon.
If you have a crafter that can repair the item and apply the powder that would be even better. If not, just say which shard you are on and I'm sure one of the fine folks around here can help you out with a deed and the powder
