I find taxis in SIN very good value, so even with the surcharge it's not really something I think about before getting in. Taxis are my primary mode of transport (partially due to my laziness).

A couple of useful tips are to call for taxis (there is an 'all-taxi' hotline, but I just use 6552-1111 for Comfort/Citycab) booking. Their system remembers you by CLI, tells you the cab number that's been assigned, and how long it will be. You can also SMS for bookings. Both of these cost a little extra ($2.50 offpeak/$3.20 for peak bookings, I think).

If you're looking for how to get to around by public transport/want to know approximate cab fare, gothere.sg is pretty useful as well. You can enter addresses or just zip codes - most buildings in Singapore have a unique zip code - and get bus/MRT/taxi directions and prices. The site also works well on mobile devices.

As for tipping - I don't, but I will round the fare up to the nearest dollar or so.