When I moved into my house the deck was all black so I pressure washed it and it will tend to raise the fibers or make the wood fuzzy, at least on softwoods. When I put the finish on, the fibers layed down but this will probably shorten the life of the finish somewhat.

Also, it tends to gouge out the areas between the grain.

If you have to pressure wash you want to use a moderate pressure machine which may be had to find.

I would use commercial deck cleaners - which ones depends on what if anything is on your deck and what condition it's in. Normally it's a stripper (some recommend it at half strength even if there's no finish on your deck) and a lightner. Brand doesn't really matter IMO since there all based on the same chemicals. These are available at the home centers.

jvan,

I would pick a stain, and then follow the recommendations on the factory website (usually more info than on the can).