Having the sensation of "skipped" or "extra" heart beats is quite common. To start, check your pulse for a full minute either at your wrist or neck. Usually you can tell if your heart rate is regular or if there are extra beats suddenly appearing. Sometimes it is a good idea for someone else to check for you as well (ie a "second opinion"). Having occasional "premature atrial contractions" is also quite common - these will give the sensation of either an extra beat or a skipped beat. If these sensations continue or are impeding your daily functioning it is probably a good idea to go see your physician as an abnormal heart rhythm can be very serious.