I do LHR-SFO every couple of months. You absolutely, positively do not want to sleep on the way out. Stay awake for the entire flight. On arrival, have a light evening meal, and then take a little stroll around the city to keep you awake and sharp for a while. When it's 9-10pm PST then retire to your bed. You'll be very, very tired, but you'll sleep well and shouldn't wake up at 3am, which is what tends to happen if you either sleep on the plane or go straight to bed on arrival.

Don't go overboard with the alcohol on the plane too - take plenty of water onboard.

It's a long old slog, and you'll be shattered by the end of the day, but it is completely worth it from the point of view of not ruining the rest of your trip with 3AM wake ups and being zonked by 7PM.