Also, get a damp sponge and wipe your hot soldering tip across it.
The tip gets oxidized after a few minutes in air when hot. Wipe it across the sponge with some light presssure each time you are going to make a joint. Wait about 5 to 10 seconds after wiping for the iron to reheat a bit. Then touch the pin you want to heat (or better, touch the pad you want to heat, then apply solder to the pad/tip interface.
You should have a nice, bright and smooth connection.
If your wire or component leads are old (many years) or dull, use a pencil eraser or ScotchBrite pad to remove oxidation.
Any oxidized can cause the solder not to "wet-out" on the pad or component surface. If the solder beads-up instead of wetting out, you have an oxidation problem.