San Francisco is a pricey city, but you can enjoy everything it has to offer on very little money. You can find free attractions, save on getting around the city, and even find affordable lodging in Union Square, if you know where to look.
Where are you staying? The big question is: are we looking for a hostel or a hotel? A hostel will be cheaper per night. It will also help you with food costs. Most hostels have a kitchen, so you can hit a grocery store or even heat up leftovers. However, it might not be your cup of tea. Big chain hotels in Union Square or in Fisherman’s Wharf can be pricey, but there are some non-chain “budget” hotels that can work too. Do your homework before you book one of these hotels. Some hotels (Like the Adante or Hotel des Artes) are wonderful. Others are just run down and are more prone to transients. Make sure the hotel is close to Union Square proper or in Nob Hill. The Tenderloin, a not so great part of the city, is only a few blocks away from Union Square. Never take the hotel's oficial website or own review at face value. Always look for previous guests reviews.
Choose your airfare. The best way to find airfare deals is online. You can acheck individual airlines, use services like Expedia or Priceline, or you can use a search engine like Kayak. Kayak searches serveral of the online travel sites and individual airline websites to find the cheapest flights available. Once the site returns the results it sends you directly to the webste to make the purchase. Kayak does not search all the airllines. Southwest Airlines does not always show up in the results, so you may wat to do a little bit of mixing and matching.
Finding food. Look on sites like City Guides or City Search. Under the restuarants link you should find somthing that says cheap eats or you should be able to sort restuarants by price. This will give you and idea of where you can get Meals with out breaking the bank. Obviously, places like The MIssion are going to ahve inexpensive Mexican resturants. Chinatown will have great deal on Chinese food. There will be place at Fisherman's Wharf that have specials on off peak days. Union Square evven has some hidden gems. Just walk around and you can find pizza places, chinese, irish pubs and fast food that is all affordable. You can also use these sites to find deals and insider's secrets for resturants. If you do want to splurge on a nice meal, you may be able to find specials and discounts online too. Also, ask the hotel front desk, they may have coupon books or personal reccomendations. Social networking sites like Thorntree or Trip Advisor may be helpful too. Do a search and see what you find. Thorntree is a resource for backpackers, so it will most likely have sheap food tips for most major cities.
Ditch the rental car. If you are staying in the city, rental cars are pretty much a waste. Parking is expensive and sometimes hard to find. Save the rental and parking fees and get a MUNI pass instead. You can put money on the car or you can get passes for certian amounts of days. These passes give you unlimited rides for the days the pass is valid. You can order these online ahead of time, or you can buy one once you arrive in the city. The MUNI system can get you just about anywhere you need to go. Even if you have to take a cab (this usually applies to late night travel), the city really isn't that big so the fares usually are low. If you are venturing outside the city, the public transportation may not be as reliable. In those cases only have the rental car for the day or days you will be out and about.
Find Free or low priced Attractions: Once again use the power of the internet. Using the keywords "Free attractions San Francisco" with a search engine will bring up many hits. You can also look online for couplons and discounts. Sites like CitySearch usually have a free attractions link or you can search event listings and use free as one of the sort options. Once again Thorntree will also be a great source. Always dsearch for your question first. Thorntree already has an extensive collection of San Francisco travel tips for backpackers and budget travelers. Also check there before asking a question. If your question is not listed, then ask the forum. Always make sure your question is specific and you list who you are, your age, your interestes and who you will be traveling with. Of course, always check out the brochures and materials at the hotel or hostel, and you can always ask the front desk staff.