off the top of my head:
go up Twin Peaks for a view of the city
walk the Golden Gate Bridge, maybe all the way to the observation area across the Bay to look back to the city
visit Alcatraz
visit the Painted Ladies houses
not sure if they still allow tours right now, but if they do, visit the US Mint
Cable Car Museum
ride the Cable Car all the way from the Market Street turntable to the end of Fisherman's Wharf
walk up Lombard Street to see the famous hairpin turns (one of the Cable Car lines actually has a stop on the top of Lombard, so you can get off there instead and then walk down instead of climb up, making it easier)
Palace of Fine Art
Cliff House/Sutro Baths
Coit Tower
check out Saint Mary's Cathedral. when they allow entry, the inside is great for photo
take a boat tour of the bay. Blue and Gold on Pier 39 or Red and White on Pier 43 are both good
if you're at Pier 39, check out the sea lions that's sun bathing just off the pier
and if you're into that sorta things, go check out the SF City Hall. not sure if they allow visits inside at the moment but it's very beautiful and perfect for photos, seeing it's the most expensive city hall in the US
the Dragon's Gate at one end of China Town
food wise, there's also a lot of choices
Swan Oyster Depot
Tony's Pizza Napoletana
Hot Sauce and Panko To Go
Li Po Cocktail Lounge
Yee's Restaurant
Panchita's Restaurant
Boudin Cafe over at Fisherman's Wharf (pretty sure they have stores at both Pier 39 and 43
outside of these, your friend probably knows a lot more good eats.