I'm ready to start experimenting with transistors, but I've read a lot about how easy they are to fry. I'm not very well funded and I can't afford to keep buying new transistors. I'm getting most of my parts by unsoldering them from PCBs in old electronics. So far its been working great, but I tend to have issues knowing how much electricity I can put through things. So far I've been doing things by trial and error, but I think if I do that with transistors I will quickly run out of parts. I have all the basic tools. Soldering iron, continuity tester, multimeter, etc.
I have a robot, but its entirely remote controlled so its more of an RC car that looks like a little robot for now. I made its controller by taking an old remote control, drilling through the PCB around the buttons directly on the copper lines, and soldering a wire in so when the button is pressed, current goes through and the robot moves. The harder the button gets pushed, the faster the bot goes. The problem is, even pushing so hard the controller is about to break, it still has a lot of resistance and the robot doesn't go nearly as fast as it would if it was wired straight from the battery to the motors, without the buttons. I just really need to know how to use transistors without frying them.