Good advice, TJ---all of it. Ian, just because it's a good opportunity to lay down a "how to solder" post, I'm going to pretend you know less about it than you do, so please forgive me. Your patience will allow me to be wordier. *L* Thanks!
For beginners: soldering is not like glueing with hot metal. You are using heat to get several metals to create a molecular bond, not just stick together. So, some basics:
1. Clean your soldering iron tip first. You can accomplish this (and reclean as you go) simply by letting it heat up nice and hot, then wiping the tip against a wet sponge. I realize you may think this will melt the sponge, but it won't. Immediately afterwards, melt some solder against the tip of your soldering iron so it's coated with nice, shiny metal that conducts heat well. This is called tinning the iron because solder is a mix of lead, tin, and other metals.
2. Make sure your surface is clean and the metals are items that will bond with solder. Copper, brass, and any alloys of the two will bond; stainless steel and iron will not. Sorry, but that's how it works.
3. Mechanical attachment comes first: loop the wire through the eyelet, twist two wires together, or whatever it takes to get the thing attached before you solder. Try not to make the joint depend upon solder, alone, because solder can break off.
5. Flux. Flux is a chemical compound that is applied before you solder. It cleans the metal. Use it if you have it. If you still are having trouble, invest in some: it's cheap.
6. Choose your solder. There's solid solder for plumbing, rosin core for electronics, and acid core for sheet metal or plumbing: it's not what you want. It will eat at your connections long after you're done.
5. "Heat from below" and "Heat the work, not the solder" are the two best sayings to learn from. If at all possible, get the tip of your iron underneath and let the heat rise through both items. That way, by the time the solder is hot enough to melt, both items you are trying to connect are hot enough, too. So, heat the pickup plate where the wire is attached, and let the solder press against the top. As it heats, the flux will sizzle and smoke, cleaning your surfaces. The heat will rise through the plate and heat the wire, then heat the solder, which will melt and flow down through the wire to the plate and leave you with a pretty, shiny new connection.
Finally, if none of the above is happening, your soldering iron is probably too small. Weller makes a pistol-style soldering iron which has it's flaws, but it's probably the most popular and has adequate heating ability. Best of luck!