The secret to soldering is to have enough heat at the point of contact for just the right time--and scrupulous preparation.

The latter means you should scrape, sand, or steelwool the surface to be soldered, and then clean it of all oils, residues, and contaminants--including fingerprints. I use denatured alcohol for this, after I make sure the surfaces to be joined are shiny.

Never carry the solder to the work on the soldering iron tip! Always heat the work and add the solder to the work at the same time. The use of a good rosin-core solder such as Ersin Multicore or Kester 60/40 is essential.

The flux will cause the solder to "flow." Sometimes adding just a little bit of solder to the work or the iron's tip will also cause the flowing effect. Just don't over-do it. And don't use acid fluxes where you won't be able to remove every trace later. They can cause nasty corrosion. However, I use paste flux quite a bit on larger items. I clean it off with denatured or 99 percent isopropyl alcohol.

Also, use a wet sponge to keep the iron's tip clean. I clean the tip by swiping it on the sponge before EVERY joint is made. Then I add a miniscule bit of solder to get the flux flowing and keep the tip "tinned." I also use steel tips, not copper. If you use copper, you can "dress" the tip with a file every now and then as needed. Do NOT file or dress a stainless tip! You'll ruin it, and they're expensive.

Sometimes, with larger pieces, or items you're going to "sweat solder" together, it pays to pre-coat the surfaces. This is called "tinning." Just prepare the pieces, and coat them with a thin solder "plating" before joining them with extra solder. Oftentimes you'll tin a job before putting it into place with the other piece to be joined.

Sweating two pieces is nice because you don't see the soldered connection or joint. The two pieces are previously tinned and then placed together and then heated until the solder on the hidden surfaces flows together.

Also, once the solder is joining the work, be sure not to move the pieces until the solder cools and sets. If you see a grainy effect, the soldered connection is said to be a "cold" solder connection. Re-do it! Do not cool a joint with water either. Let it set or cool naturally.

You can use a "solder sucker" to remove excess solder or to de-solder something, or try solder wick. Solder wick is a copper braid that sucks up solder, but it needs a little added flux-based solder to make it "start." I prefer a solder sucker, but they're much more costly. The solder sucker is a spring loaded affair with a trigger and a heat-resistant tip. You place it on the molten solder and hit the trigger and---bingo--the solder gets sucked into the tool, leaving a clean (and usually tinned) surface!

Here's a site with some tips on soldering and un-soldering. http://www.morsex.com/building/atoz.htm#Soldering