I put one of those switches inside my brake leaver, its a switch that is reversed, so when you push it is kills the circuit. That way when i apply the brakes even just a tad, the circuit is closed and my brake lights light up.
I use a radio shack iron, does what i need. I let the iron heat up in its stand, tin the wire, and sometimes I may tin the part, if there is plastic that'll melt easy. For those switches, a pair of helping hands is nice, you can clamp the wire and switch down.
I think the hurdle I faced with soldering was heating the part, just sortof figured the solder would just stick there.
This guy seems to explain most of the points I would mention
YouTube - How to Do It: Basic Soldering