wow, first and foremost, thank you all very much for giving me such valuable information, gotta print it out for reference^_^ (mannual doesn't have such clear explaination, it only tells you how to change the settings) I've tried spent lots of time taking pictures with different combinations of parameters on the same object, although I can tell there're differences, but it's still difficult to comprehend these stuff.
So basically a tripod is what I need for night shots, rite?! I'll then need to use a longer shutter speed to capture more lights and a suitable ISO speed to balance the brightness and noise (and turn off the flash). rite?!
Sorry I just came up some more questions...
This question might not be smart but..just wanna ask..., what's the best parameter for taking night shots (or places with insufficient light) if I don't have a tripod?
How about if I wanna take a night shot with someone in it? If the flash is off then it'll be too dark to see the face of the person.
What about if I'm facing a strong light source (like sun light during day time), would adjusting ISO and shutter speed help produce a higher quality photo? since I think simply using the flash makes the picture looked unnatural (looks like the object is copy-and-paste on to the background)
Last Q is how about taking a shot on sports or car racing...etc something that is moving?
Thank you all again, these are some questions that burdens me for some time, thanks and I'm really appreciate of your help.