Probably starting in LA and heading North to possibly Vancouver.
What are the places our things not to miss?
We are a young group of 4
Definitely drive up the Pacific Coast Highway. Make sure you hit up Big Sur during the daytime. It's a waste of an incredible view if you hit it at night. Maybe camp for a day or two in the forests near there. PCH will take you straight into SF, and you can obviously find a ton of stuff to do there. In Nor Cal you can find Sequoia National Park and Yosemite, but they're a bit out of the way, if I recall. Beyond that, I think a good guideline is to stick near the coast. about 6 years ago
Absolutely agree with Big Sur. Don't for a second even consider taking the 101. Its Number 1 all the way.
For a feeling of fulfilment you could start at San Deigo, or even Tijuana and then you'll have done the entire "West Coast". I found every damn National Park of the US the greatest places the country has to offer, so if you can swing by one or two, it just adds a huge dimension to your trip. Sequoia or Yosemite or Joshua Tree. But these should not be making you detour too far off Number 1 baby.
The whole "North West Pacific" which in my mind includes Seattle and Vancouver is all amazing, so whether you want to finish off in Whistler Canada and maybe Vancouver Island, or Olympic and Mt Baker National Parks around Seattle, make sure you see one of them through, don't just burn up the I-5.
San Fran, Seattle and San Diego (in that order) are my favourite places on the west coast. LA on the other hand is a soul-less beast with only Santa Monica worthy of a mention.
Check roads are open in the mountains if you do head off the coast, as snowfall is unpredictable.
And pack lots of snacks!!! about 6 years ago