1. Before doing any work to your deck wash away all dirt and wood fibers first. This can be done with a power washer and a mild detergent if necessary, remember when working with the pressure washer to keep the pressure low enough to not gauge the wood.
2. Fix a popped nail by removing it with a cats paw and then reattaching the board with a screw longer than the nail you removed. Care should be taken when using the cats paw to not damage the wood, using a shim between the cats paw and the decking baord can help prevent any damage to the board.
3. Stain and seal your deck to protect it from moisture and the suns UV rays. Using a clear stain will allow you to not change the color of your deck, select a stain that has UV protectant in it. If you wish to add color to your deck then select a semi-transparent exterior stain in either latex or oil base. After you have stained your deck allow it to dry for 48 hours and then apply a sealant.