Singapore is one of the more expensive countries to visit in SE Asia. If you are coming from another country such as Thailand or Cambodia, the price shock will be pretty severe if you aren't prepared. However, this doesn't mean that you can't afford to visit for a week or more. Here are a few budgeting tips to help you save a bit of cash:
1. Using the metro in Singapore is a great idea. The roads aren't really pedestrian friendly, and the city is rather confusing to get around in. While walking to China Town, I once asked a uniformed police officer for directions, and he didn't know the way! Most locals don't really walk from place to place, so if you're in a hurry you're better off using the underground metro. Every ticket that you collect, save them as you can deposit them later at a machine for a small refund.
2. There's a foreign exchange currency booth at the Changi International Airport, but don't change more than absolutely necessary here. The rate which is used at the airport is far higher than the rate used by the foregin exchange companies downtown. I changed $50 USD at both the airport and downtown, and for the latter, I received almost $3 SGD extra.
3. If you have a flight departing on a budget airline such as Tiger Airways, these airlines don't operate at the main airport. You have to take the metro to the Changi International Airport, then go to the basement floor to catch a bus to the budget terminal. You will need to buy a ticket from the booth at the bottom of the basement stairs, then follow the signs to the bus stop. I didn't know this in advance, and as a result, I almost missed my flight.
4. Shopping in China Town is a cheap alternative to the expensive malls in the city. The prices are relatively low and if you think that an item is overpriced, the merchants are usually willing to negotiate a cheaper cost. If they are being difficult, simply walk away. Chances are, another store a mere 10 feet away may have the exact same product for a more reasonable fee.
5. Singapore has an extensive bus system, which covers areas of Singapore which are unreachable with the metro. Fares depend on the distance being travelled, but are overall very cheap. There is an online bus guide which tells you the bus numbers for the various routes, so with a little bit of homework, you won't ever need to take a taxi during your stay.