For people visiting the bay area and looking for some options for things to do, I'd like to offer this itinerary that I created for my friend as a basis for his trip.  I've included options with varying price points for activities and restaurants so that you can decide just how much you want to splurge.  And, it hits up the major sights and attractions without packing too much into a day.  Enjoy!

Don't forget your cameras for Day 2 because that's when you'll see some of the most amazing sights that San Francisco has to offer.

Ghirardelli Square is always fun to walk around.  You can also learn a bit of history by reading the historical information located everywhere.

The Palace of Fine Arts is a very popular place for weddings and weekend picnics.  You can see why from the picture above.  It's just an amazing site.  While here, you can also check out the Exploratorium.

What trip to San Francisco would be complete without going to see this famous icon?  You can choose to walk/bike/drive across the bridge to Marin County.  Or, you could choose to view the bridge in all its glory from the nearby Presidio or Fort Mason areas.  Both areas provide some stunning views of the bridge and you can find many trails that allow you to take some great pictures.

For dinner, I recommend the House of Prime Rib for those with hearty appetites.  The picture above is NOT from the restaurant.  But, you can see some great pictures from their site here - http://houseofprimerib.net/.

Day 3 is all about visiting the famous prison on Alcatraz Island and the piers.

You'll need to take a ferry there.  Entrance to Alcatraz is free, but there is a fee for the ferry.  Book those tickets early to ensure that you have a seat.

Once you've had your fill of Alcatraz, you can visit a few of the attractions back on the San Francisco peninsula.  A few major attractions along the piers include the Ferry Building Marketplace and Fisherman's Wharf.

The Ferry Building is a terminal for ferries that travel across the San Francisco Bay to the East Bay.  It also includes a shopping center and some great restaurants.  On the top of the building is a large clock tower that was modeled after the 12th century Giralda bell tower in Seville, Spain.  The clock tower chimes every full and half-hour.

Fisherman's Wharf plays host to many San Francisco events, including a world-class fireworks display for Fourth of July, and some of the best views of the Fleet Week air shows.

Don't forget to say hi to the sea lions at Pier 39.  Pier 39 is a shopping center and a very popular tourist destination.  There are plenty of shops, restaurants, a video arcade, street performances, an interpretive center for the Marine mammal center, the Aquarium of the bay, 3D rides, and the famous sea lions.  From the pier, you also get great views of Angel Island, Acatraz, the bay bridge, and the Blue and Gold Fleet's bay cruises

Day 4 is your day to take some time and enjoy nature by relaxing in Golden Gate Park.  There's plenty that you can do.  Here are just a few things to keep an eye out for:

Stow Lake surrounds the prominent Strawberry Hill, now an island with an electrically pumped waterfall.  Rowboats, pedalboats, and electrically powered boats can be rented at the boathouse. Much of the western portion of San Francisco can be seen from the top of this hill, which at its top contains one of the reservoirs that supply a network of high-pressure water mains that exclusively supply specialized fire hydrants throughout the city.  You can also rent bikes here to get around the park. 

The Japanese Tea Gardens is also immensely popular.  It is said that the fortune cookie was invented here.

Spreckels Lake is located on the northern side of the park near 36th Avenue. As the home waters of the San Francisco Model Yacht Club, one can usually find model yachtssailing on Spreckels Lake. Many of these are of the 'free-sail' type used before the advent of the modern radio controlled models.  

The famous windmills in Golden Gate Park.  In 1903, a pair of Dutch-style windmills were built at the extreme western end of the park. These pumped water throughout the park. The north windmill has been restored to its original appearance and is adjacent to a flower garden, a gift of Queen Wilhelmina of the Netherlands. These are planted with tulip bulbs for winter display and other flowers in appropriate seasons. Murphy's Windmill in the south of the park is currently being restored.

The De Young Museum exhibits American decorative pieces, textiles, and paintings from the Rockefeller Collection of American Art.  It is home to the annual floral exhibition  Bouquets to Art.  Other permanent collections include the African and Oceanic collections which, along with the 'Art of the America's' collection, were curated by Kathleen Berrin.

The California Academy of Sciences is one of the largest natural history museums in the world, and also houses the Steinhart Aquarium and the Morrison Planetarium. The Academy of Sciences carries exhibits of reptiles and amphibians, astronomy, prehistoric life, various gems and minerals, earthquakes, and aquatic life. A completely new building for the Museum opened in September 2008.

The Conservatory of Flowers is one of the world's largest conservatories built of traditional wood and glass panes.

The San Francisco Botanical Garden at Strybing Arboretum is a 55 acre (222,500 m²) arboretum that contains more than 7,500 plant species. The arboretum also houses the Helen Crocker Russell Library; northern California's largest horticultural library.