usually, when I solder a through hole pad, I do these, about half a second or a second apart:

* Touch the soldering iron to the pad, let it heat
* Then add solder to the PAD, not to the iron (or at least, where the iron is touching the pad. You should see the solder "flow" around the pad
* Then adjust the iron slightly to make sure it's making good contact with the PIN, you'll probably see the solder wick up the pin a little better
* remove the iron, make sure it looks "smooth". If not, gently place the tip back on, touching the pad and the pin, until it all goes smooth