Use screws, sand the wood, use a quality stain. Take your time.

Wash, replace bad boards, fasten loose boards with screws.  Nice weekend project,  paint out stain to tast.  It is your deck or are you prepping for sale. It it were mine, I’d check into synthetic wood.

Deck screws are a must.  Replace bad wood, sand all the wood and use a high quality stain & sealer.  I'm sure Debbie Gartner could recommend a good product to use.

I'd use screws, never nails.

I'd go with a high quality solid or semi-solid stain.
I would not use transparent sealers, otherwise you'll be doing it every year.

I was always for wood, but gave in to Trex as it is SO much easier to care for. Our cedar deck rotted away. We didn't want to use pressure-treated wood due to the arsenic component, especially with children around. Previously had used red wood, with screws and hubby covered each hole with a red wood plug to make the deck perfectly smooth. That was when the children were very little; no splinters.

Sand it first to get the dry, weathered part off before painting or staining so it soaks in evenly to protect.

Fred,

Screws, and high quality stain.  A

We've done this a few times with renovations. Agreed, always screws. Some boards may need to be replaced. Sanding may be required, depending on condition. Pressure wash, let dry fully and stain. Some prefer clear, if the wood is two colors, I'd suggest a stain with color or full color stain. Test a few hidden spots for color if desired to ensure you're happy with the look before staining the entire deck. 

Screws to secure, power wash to prep it for a drink of oil.. stain but never ever paint. The deck is the outside living room and pretty important area if you are parked on the water, big view, etc.

Screws and deck stain.

Agree with Wanda Kubat-Nerdin - Wanda Can! Sand it first. 

Then use a high-quality stain.  IMHO...painted decks need more maintenance

I am a fan of screws in decks ... stain not paint. 

I just went thru this with my parents deck. It was stained & parts of it were a disaster with peeling. Not sure why it was happening. 

Since you didn't build the deck, I'd be sure there were no nails that could work their way out & kill your feet.

I think the deck looks ok. I'd just clean it with that deck wash they have now.

Wow Fred you are one busy guy! I have no idea.....

At a recent home inspection my buyers, the inspector and I were discussing how to best prolong the life of the existing deck to focus on other projects first. 

The inspector offered a brilliant - IMHO - solution: carefully remove the boards and flip them upside down! The other side will often show much less wear and tear than the one that had been exposed to the elements for years. Then you can decide if you want to leave it natural, stain and/or use a product such as Deckover for a smooth finish and to prevent splinters.  

Only screws and TREX decking...no stain or wood rot.

Eve

We just did this with the deck at our home. We replace the decking with a manufactured wood ($5.25/linear foot) that doesn't need painting then replaced the railing with an acrylic railing system. This Spring we will build a small patio and move the grill off the deck and onto the patio. We used clips to join the decking and galvanized screws where necessary