Before You Leave
... get a guide and a set of maps.

'Lonely Planet : California : Life Is Great in the Golden State (Lonely Planet California)'
is a good starting point, as are most guides from that series.
If you're a member of AAA, I also strongly recommend you to get the current edition of the club's California Tourbook - it's a great resource. As for maps,
'Thomas Guide California Road Atlas: Including Portions of Nevada : Spiral (California Road Atlas)' is pretty unbeatable for a comprehensive, detailed collection.
(If you're planning to spend any extended amount of time in a city, you may also want to think about investing in one of their city street atlases.)

Must-Sees
Way too many people still just go city-hopping: L.A., San Francisco and a quickie side trip along PCH and/or to Yosemite National Park or Napa Valley. That, in my view, is a crying shame. Oh, not that there's anything wrong with those places - I love them all. Dearly. And yes, that *does* include my former home Los Angeles, which contrary to popular belief is not just about Hollywood, congested freeways, smog, Botox and blonde beach beauties. But from California's desert south to its redwood forests and high sierra, the state has so much more to offer! So if you truly want to get to know California, put these places (and book recommendations) somewhere near the top of your list:

'The Explorer's Guide to Death Valley National Park (Travel and Local Interest)'
'Joshua Tree: The Complete Guide: Joshua Tree National Park'
'Frommer's San Diego 2006'
'Catalina Island Handbook: A Guide to California's Channel Islands'
'Lonely Planet Los Angeles & Southern California (Lonely Planet Los Angeles & Southern California)'
'San Bernardino Mountain Trails: 100 Hikes in Southern California'
'Santa Barbara and the Central Coast, 3rd: California's Riviera'
'Day Hikes San Luis Obispo County California (Day Hikes)'
'Hearst Castle: The Biography of a Country House'
'The Monterey Bay Shoreline Guide (University California Press/Monterey Bay Aquarium Series in Marine Conservation)'
'Hiking Sequoia and Kings Canyon National Parks (Hiking Guide Series)'
'Hiking Yosemite National Park, 2nd (Hiking Guide Series)'
'Lonely Planet San Francisco (Lonely Planet San Francisco)'
'The Napa Valley Book: The Insider's Guide for Visitors and Residents'
'Backroads of Northern California (Pictorial Discovery Guide)'

California Dreamin'
- or: What to watch and read when you're back home ...

NATURE:
'John Muir : Nature Writings: The Story of My Boyhood and Youth; My First Summer in the Sierra; The Mountains of California; Stickeen; Essays (Library of America)'
A must-read, even if you don't look at anything else.
'Mojave Desert Wildflowers: A Field Guide to Wildflowers, Trees, and Shrubs of the Mojave Desert, Including the Mojave National Preserve, Death Valley National Park, and Joshua Tree National Park' (This is also a good one to bring.)
'Cougar: The American Lion'
'High And Wild: Essays And Photographs on Wilderness Adventures'
'Yosemite:Fate of Heaven'
'Big Sur & Beyond: The Legacy of the Big Sur Land Trust'
'The Western Horizon'

HISTORY AND LIFESTYLE:
'The Elusive Eden: A New History of California'
'Ghost Towns and Mining Camps of California: A History & Guide (Historical and Old West)'
'The Fight in the Fields: Cesar Chavez and the Farmworkers Movement'
'Casa California: Spanish-Style Houses from Santa Barbara to San Clemente'
'San Francisco Victorians'

California in the Arts
Don't ever tell me that California doesn't have an arts scene outside of Hollywood. That's part of it, of course, but it doesn't end there - not by a long shot. Here are just a few examples ... actually, the list is *much* longer than this.

MUSEUMS AND FINE ART
Both San Francisco and Los Angeles have a number of excellent museums and art galleries. At the very least, have a look at
'Museums of the San Francisco Bay Area (Eldan Press Museum Guidebook Series)' and
'The J. Paul Getty Museum Handbook of the Collections (Getty Trust Publications: J. Paul Getty Museum)'.
(Actually, the Getty and the museums in San Francisco's Golden Gate Park are almost worth a visit for their stunning locations alone - not to mention the Getty's architecture.)

LITERATURE AND THE MOVIES
- seem to go hand in hand in California more closely than elsewhere, but that's not necessarily a bad thing (at least as long as literary output isn't merely some sort of afterthought-print version of the latest box-office blockbuster). California has a proud and excellent literary tradition, and more often than not it is the quality of a piece of fiction writing which then also inspires an equally outstanding movie. To wit:

JOHN STEINBECK
Nobel laureate, Pulitzer Prize winner and undisputed king of Californian writers
'John Steinbeck: The Grapes of Wrath and Other Writings 1936-1941: The Grapes of Wrath, The Harvest Gypsies, The Long Valley, The Log from the Sea of Cortez (Library of America)'
'Steinbeck Novels 1942-1952: The Moon Is Down / Cannery Row / The Pearl / East of Eden (Library of America)'
... and the immemorial movies based on his works, such as
'The Grapes of Wrath'
the depression-era story of the Joad family, migrant farmers from Oklahoma, starrring Henry Fonda, Jane Darwell and John Carradine;
'East of Eden (Two-Disc Special Edition)'
the modern-day Cain and Abel story of Salinas farm boys Cal and Aron Trask, starring James Dean, Raymond Massey, Richard Davalos, Julie Harris, Burl Ives and Jo Van Fleet;
'Of Mice and Men'
and the heartbreaking tale of itinerant workers George and Lennie, starring Burgess Meredith and Lon Chaney Jr. in this 1939 adaptation (there's also an excellent 1992 versionstarring Gary Sinise and John Malkovich).

THE NOIR TRADITION
- including but by far not limited to:
'Crime Novels : American Noir of the 1930s and 40s : The Postman Always Rings Twice / They Shoot Horses, Don't They? / Thieves Like Us / The Big Clock / Nightmare Alley / I Married a Dead Man (Library of America)'
Part 1 of the Library of America's 2-volume collection of noir literature. (Also check out the series's entries containing the works of Dashiell Hammett and Raymond Chandler!)
'The Maltese Falcon'
After a number of tough guy roles, Humphrey Bogart was (re)born as the ultimate noir gumshoe in John Huston's adaptation of one of Dashiell Hammett's most famous Sam Spade mysteries.
'The Big Sleep'
Bogart & offscreen wife Bacall created movie magic in this William Faulkner-coscripted adaptation of Raymond Chandler's first Philip Marlowe mystery, directed by Howard Hawks. Not even Chandler himself could unravel the labyrinthine plot, but frankly, my dears ...
'Chinatown'
A modern milestone in noir history, starring Jack Nicholson and Faye Dunaway and directed by Roman Polanski: The story of the 1940s' water wars; freely based on the work of William Mulholland (for a factual account, see 'William Mulholland and the Rise of Los Angeles'.)
'L.A. Confidential'
A standout in California's rich modern mystery scene, finally, is neonoir writer James Ellroy, whose novel about a trio of bad cops wanting to do good was adapted in this highly successful, stylish movie starring Russell Crowe, Kevin Spacey, Guy Pierce, Kim Basinger and Danny DeVito.

THE BEAT GENERATION
San Francisco's literary revolutionaries:
Jack Kerouac ('On the Road')
Allen Ginsberg ('Collected Poems 1947-1980') and
William Burroughs ('Naked Lunch: The Restored Text')
- to name just three. (Plus Lawrence Ferlinghetti, Gary Snyder, Neal Cassady, Gregory Corso, Diane Di Prima, Ken Kesey, Michael McClure and Los Angeles skid row poet Charles Bukowski.)

MUSIC:
'Stravinsky: Firebird, Rite Of Spring, Persephone / Tilson Thomas, San Francisco SO'
San Francisco's Symphonic Orchestra is world-renowned, and for a reason - with or without star conductor Michael Tilson Thomas.
'Joshua Bell ~ Sibelius · Goldmark - Violin Concertos / Los Angeles Philharmonic · Salonen'
But I was more than happy with the productions of the Los Angeles Symphonic as well.
'Central Avenue Sounds: Jazz in Los Angeles (1921-1956)'
L.A. also used to be a fixture on the jazz scene ...
'Made in California'
... and of course, California produced a whole range of legendary rock bands and musicians, such as the Beach Boys, The Mamas & The Papas, Jefferson Airplane and one of my all-time favorite bands, The Eagles, who wrote *the* definitive song on 1970s' Golden State culture:
'Hotel California'.

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California is also making more and more of a name for itself in the culinary field.

For suggestions where to eat while you're there, see my L.A. AND SAN FRANCISCO RESTAURANT GUIDE (copy and paste this link into your browser):
http://www.amazon.com/exec/obidos/tg/guides/guide-display/-/3LE5OI4B2605R/

If you're interested in COOKBOOK SUGGESTIONS, you'll find plenty of those in my "Culinary Trip Across the United States" guide:
http://www.amazon.com/exec/obidos/tg/guides/guide-display/-/23AM9TR05O6G2/

Savor and enjoy!