Mirror, signal, shoulder check, move. These are the four steps for a successful lane change. Simple enough one would expect, until you watch what goes on around you in traffic today. This is a basic skill that a driver should be confident practicing once they have left the novice stage behind.
Unless a lane change is forced by an emergency, the first step in changing lanes is to think ahead and plan your move. Scanning well in advance for changes in traffic or anticipating your exit gives you the time to execute a lane change safely, without affecting the travel of another vehicle.
If you've left yourself an out, you can minimize the risk in an emergency as well.