Yip, as 45-110 says, there are other threads on this if you want to read more about it. But here are a few pointers to briefly answer your questions.
(1) If you are gonna make a spring, then it's good to taper the spring steel in both it's length and thickness, as having that kind of taper helps the spring function without breaking. So, make it a little more narrow toward the free end. Leave enough "meat" on the wide end to put in a screw or however you plan to mount it, and then come out away from that before you start the taper. And mount it in such a way that the part that has the screw hole in it won't be bending at all, or it will break there.
(2) In forging a small piece of spring steel using a torch, just go to a red heat. Use multiple heats if necessary. Also just go to a red heat when hardening. To harden, just go to the red heat and then quench. Oil is fine for this. To temper, first clean the colored scale off with sandpaper and then heat it again slowly, going to blue. If using a torch, you can quench it again to stop it at that point. That's just to cool it quickly lest you accidentally get it too hot.
If tempering on the eye of the stove, I just slowly raise the heat while watching the color build over 10 minutes or so, and then just take it off when it reaches the color I want.
(3) If using a handsaw blade, if you don't need to bend it or put a curl into the end, then you don't need to heat or temper it at all. It's already soft enough to cut with a hacksaw and files, but hardened enough to work as a spring. If you want to put a curl in it, you will need to heat it to bend it, and then harden and temper it.
