For someone starting out it helps to get an old piece of electronics to practice on. Lots of old vcr's, radios etc being dropped off at e-waste sites.
Too much heat and you can lift copper traces and damage components. Too little and you get a poor quality joint that can cause intermittents. Just takes practice.
Also some boards such as the cruise modules have a lacquer conformal coating that has to be removed or you get contaminated joints.