This is how I desolder components.
First, I add additional solder to the pads. I know it sounds counter-productive, but believe me it makes the desoldering job easier by adding some fresh solder to it.
OPTIONAL: If you're desoldering a multi-pin component, and you don't mind sacrificing the component, go ahead and cut the leads. This makes the desoldering job also easier.
Next, I add some liquid flux to the pads I. So the pads now have additional solder, and flux. The flux helps spread the heat and also makes the solder more "liquidy" so it flows easier.
The right tool can make the job so much easier. Here, I'm using a Hakko 936 desoldering gun. One of the BEST investment in tools I've made. Give it a few minutes to heat up. Also make sure the gun's holes are not clogged.
Place the tip of the desoldering gun on top of the pad. When the solder starts to melt, pull the trigger. The desoldering gun will suck it up. While sucking, move the gun around the pad. Don't push down hard or you may scratch the PCB.
Here's a photo of the sucked-out clean holes.
As you can see, there is flux all around the area. We need to clean it up. Use alcohol and toothbrush for this job, then damp-dry the area.
Here's a photo of the area after cleaning with alcohol.
Now you can insert your new component and proceed to solder it.
After soldering the new part, clean the area again with alcohol for a nice clean finish.