After heating up your soldering Iron tin the tip this is done by melting a small amount of solder onto the tip and helps to transfer heat to the joint.
When soldering remove the solder first then the iron.
Your joint should be shiny if done correctly
Some components, such as transistors, can be damaged by heat when soldering so if you are not an expert it is wise to use a heat sink clipped to the lead between the joint and the component body. You can buy a special tool, but a standard crocodile clip works just as well
Use the right tip for the job.