How to make area under deck dry?

There's a product called Dry-B-Lo under deck system. Lowe's sells a cheaper knock-off, but I'm sure it works the same.

If you are storing something there, the best thing is to use tarps or keep everything in a plastic container that is weather proof. Unless you are going to cover up your deck so that nothing trickles down through the gaps in your boards, you need to provide a water-proof barrier between the stuff coming down through the deck and the dampness from under the deck.

Exactly! Roxaneg is right. Dampness comes from above and below the deck. You could try a water barrier on the ground and over the deck, but I think using water proof container for storage will work better. The entire ground around the deck is damp from rain or even dew. You can't keep that from seeping under the deck. Plus you won't enjoy your deck if it always has to be covered. If it's a LOT of water, you might be able to install a drainage system to get the worst of it but it will always be a little damp.

We have rocks and pavers -having a dog -thats a great buffer as you dont drag as much dirt/mud.

Prior to the remodel we had pea gravel which might be more attractive - but it often got stuck in athletic shoes which is a hazard to hardwood floors.