so when i drive normally, i shift up when my rpm hits 3000 rpm, and i shift down when it hits around 12000 rpm. right? and to shift, i have to let go of gas, hold clutch down then shift.
The RPM where you shift up/down depends on the situation (and part of the point of a manual is that
you get to decide when). Generally, yes, you want to shift up at 3000RPM for ordinary driving, although some cars can get away with 2500RPM or even 2000RPM, depending on how economical you want your driving to be. However, I should probably mention that with the S2000's high-RPM powerband you might want to shift even higher, close to 4000RPM. An S2000 enthusiast forum would be able to tell you more about that.
As for shifting down, well, it depends on what you're doing. Most downshifts you make will be because you're slowing down for a red light in, say, 6th, and then it turns green while you're still going 10mph. In that case, you wouldn't want to try to accelerate in 6th, so you downshift to 2nd and go on your way. By the way --
don't try to downshift into 1st while moving. Always use 2nd unless you've come to a complete stop.
There are other situations, too, like slowing for a turn where you don't have to stop (such as turning left from a major street into a parking lot when traffic is clear). For those situations I use a lazy form of rev-matching -- clutch depressed, move shifter to 3rd, use throttle to raise RPM (from spending nearly every day with my car I know what RPM to go to), release clutch, make turn -- but if you feel uncomfortable trying that then you could either coast into the parking lot or come to a stop before making the left turn.
Only once have I truly used heel-toe downshifting, and that was when I was doing some spirited driving on a valley road on a rainy night. A corner ended up being sharper than I had expected, so I instinctively heel-toe downshifted (hurray videogames!) and made the corner in a bit of a slide, with room to spare. It felt awesome.
i have another question. so do you have to worry about slowing down earlier since you have to watch rpm? or do you slow down as if you drive a automatic, since you drive manual and have to be more aware, you slow down earlier right?
The only thing different about slowing down with a manual is that you have to worry about putting the clutch in when your RPM reaches idle speed, or shifting to a lower gear when you're able to accelerate again and your RPM is too low to accelerate from.
Basically, all you have to do is make the decisions that the automatic used to make. Everything else about driving is exactly the same.
It shouldn't have to go all the way down in every car, but it depends really.
You should depress the clutch to the floor anyway. Shifting with the clutch half-way might work, but as I know from experience of trying it, if you don't press the clutch down far enough then you'll get some gear grind. Even if you don't hear grinding, you could still be exposing the clutch and/or transmission to some unneccessary wear. Besides, it's easy enough to press the clutch to the floor.