A quick glance at the map shows that there are quite a few grocery stores along the way and that one of your last chances to fill your gas tank is in Paia. You can even load up a My Map of points of interest along the way.
Consider another scenario, where you want to meet a friend for dinner on your way to downtown San Francisco. You search for transit directions from where you are on 24th and Valencia to Downtown SF, and then search for two of your favorite restaurants, Bar Jules and Walzwerk. Clicking on the blue bar at the bottom of the left panel reveals both searches for the restaurants as well as your route downtown. You can click on the checkboxes to turn each search on and off.