I cleaned up the wood real well, sanded and varnished the steps with 3 coats of Interlux Schooner and then added white non-skid strips, the peal and stick type. I used one wide and one narrow strip on each step. It looked great and did not creat a slip hazard. Capt. George
Capt. George's advice is sound. If however you want to keep the steps all wood, you can clean, sand and varnish the steps and let them fully dry. Tape off the non-skid pattern you want on the steps (I would allow the non-skid area to go right to the edge of the step), and varnish with (non-skid abrasive added - follow the directions that comes with the abrasive for the best results). Peel off the tape, let cure and you have non-skid without the look of non-skid tape.