Eat before you hit the Grapevine. Though the town of Gorman is nestled amidst the twisting freeway section just north of the LA basin, there's virtually no services in this area, so grab a bite and a fresh cup of coffee before you drive this section of road.
Eat lunch at Harris Ranch. Harris Ranch is a great stop on the way down I-5. It offers fresh steaks on its menu and you can also pick up a few things to eat once you've gotten to your northern destination. Be warned that you'll recognize it by the smell of the cattle fields a few miles north as you drive by.
Take a rest. I-5 offers multiple rest areas (see Resources) to stretch your legs and rest your eyes. There's public restrooms, pet areas and services for RVs at most stops. John "Chuck" Erreca Rest Area is a particular favorite spot as its a good midway point on the drive north.
Be aware of the bugs. As you drive through agricutural areas, particularly around Fresno, you'll find bugs marking your windshield at a pretty heavy rate. Clean your windshield often to avoid any visibility issues.
Watch traffic as you enter into the San Joaquin Valley. It can be very difficult to get through Stockton and the surrounding areas during peak commute times as the cost of real estate has made the San Joaquin Valley a more affordable area to live. Time your drive to avoid dodging traffic during these very busy times.
