Soldering is always about technique, but using the wrong tool won't help. I'm assuming you already have the technique. The temperature is very important for a very good connection, ~700 degrees F is a good place to start. A small amount of RMA flux will also help. The wattage is important for the mass of the metal you are trying to solder. "Heat sinks" (a large mass of metal) require a high wattage iron, small wires don't. I have given many solder tests for "qualified" people, most people fail the test. You don't need a Mil-Spec soldering job for most hobby work, but you do need to recognize a poor connection that might fail. Send me an email if you need some help with your technique.