My favorite shops are in Japantown, which has a nice collection of Asian shops for goods, from beauty products to ceramic bowls to food. Besides that, I like the Braindrops [1324 Haight St] piercing studio for jewelry and piercing-related items, since I recently got my ears pierced there.
For buying fabric and string I like a store called Discount Fabrics [2170 Cesar Chavez St] in the Inner Sunset district. Paper supplies from Japantown are really nice, especially at Asakichi Antique, Arts, & Tea Ceremony Store [1737 Post St #365]. General Bead [637 Minna St] has a great selection of different beads and jewelry-making supplies.
I always see small booths in boutiques throughout SF for independent artists, and crafters can sell their items at many small shops as long as the owner is willing. Local Take [3979 17th St] has two shops, one in the Castro and another in the Inner Sunset, that showcases products from SF artists and designers. There are also frequent street fairs for vendors, especially along Market Street, where artists just set up tents to display goods. The Etsy SF team hosts expos and pop-up crafts markets on occasion for etsy shops to show off their products.
I really like Asian pastries and dim sum, so Chinatown shops are my go to. I especially love Louie's Dim Sum [1242 Stockton St] for their mantou. Otherwise, I live next to Taravel Street so there are lots of noodle and sushi shops to visit, such as Ninki Sushi Bar & Restaurant [1439 Taraval St] and King of Thai Noodle Cafe [1541 Taraval St].
On Taravel Street, there's also a sweet cafe called Rolling Out Bakery [1722 Taraval St] that I really love -- amazing carrot cake! The Golden Gate Fortune Cookie Factory [56 Ross Alley] is pretty famous for the fortune cookies, so be sure to buy a bag or two to try them out.
(I’m still underage ^^)
Golden Gate Park  is full of natural beauty to keep you at peace while you sit and craft. Do bring a blanket or two though – it’s usually chilly! There are also lots of smaller parks scattered throughout SF, but Dolores Park is a more well-known park for socialization.
Check meetups.com for hobby and craft meetup groups for your specific interests, as there are different groups for different districts and crafts. For example, there’s the Knitting to Make a Difference group that knits warm clothing for the homeless.
You can meet new friends anywhere, really, especially if you check meetups.com for specific groups of people interested in beadwork, fiber arts, etc.
SF's well-known for its absurd hills, so you have to trek around Downtown and Embarcadero to experience the pain (and take pictures at the top -- gorgeous views!).
Walk along Stockton Street in Chinatown for plenty of cheap souvenir shops. Ride on a cablecare and keep a spare token or two. Alternatively, spend $0.51 on a pressed penny at a street machine (Fishermans Wharf [Taylor St], Chinatown).
The Exploratorium [Pier 15, The Embarcadero & Green St.] is hands-down my favorite museum to go for inspiration. The science exhibits encourage thinking about things in new ways, and I always leave feeling refreshed and inspired. Golden Gate Park  is a treasure trove of museums and gardens, so definitely check out the de Young Museum [50 Hagiwara Tea Garden Dr] and California Academy of Sciences [55 Music Concourse Dr] if you can. Also, my second favorite interactive place in SF is the Autodesk Gallery [1 Market St #200] -- so many inspiring designers using interesting fabrication technology!
My favorite non-craft related attraction is the 16th Avenue Tiled Steps [16th Ave] (also called Moraga steps). The staircase features beautiful mosaics, and the view from the top is absolutely stunning. Another steep place to visit is the oh-so famous Lombard Street.
You definitely need to take pictures at the top of the staircases mentioned above, but also parks in Golden Gate Park  deserve some pictures too. The San Francisco Botanical Garden [1199 9th Ave] and Japanese Tea Garden [75 Hagiwara Tea Garden Dr] are absolutely stunning, especially in the springtime.