Scrub brush with a bleach/water solution to clean. Let dry completely, then sand to smooth out and knock down rough spots. Clean off, and teak oil multiple light coats. I always would teak oil in the fall to allow the oil to soak in all the way over winter. Don't oil and use immediatly, the oil will track and stain the interior! Once you have it cleaned, you can usually only oil every winter (if the boat sits outside you will need to do more often) and not have clean and sand but every couple years (again, this experience is from a boat that was trailered everywhere and was kept in a garage every night, more use will require more maint)
