Building your deck may have been about aesthetics, but maintaining it is about following directions. Wood looks pretty indestructible, but it isn't. When you use a power washer or opt for a particular stain or protector, you're using powerful solvents and equipment. Deck maintenance products are designed to be used in a specific manner. Almost all of them will cause problems if they're not applied in accordance with the manufacturer's instructions.
It may sound hokey to reinforce the fact that you should read the instructions carefully on the products you use, but the fact is that not doing so can cause headaches you don't want when maintaining your deck. For example, using a pressure washer against the grain of the wood can cause unsightly cut marks that won't go away without sanding. Applying sealer in cold weather, before a rain or on damp wood could keep your deck tacky and sticky for days or even weeks -- and never net you the sleek, finished look you want. What's even worse is that any mistakes you make this year will come back to haunt you next year and the year after that. Keep it sweet and simple: Read and follow the directions every time.