For small stuff.. (basically anything electronic), a soldering pencil rather than soldering gun. Clean then tin each item to be soldered (apply some solder separately). Use thinner solder, use rosin flux as it's not corrosive. Put a metal clip or something damp upstream of what you're soldering so heat doesn't flow into it and damage something.
If it's surface mount components (electronic so small the components don't even have wire leads going into the circuit board), leave that for a pro.