How can you tell if you are experiencing heart palpitation?

Heart palpitations by definition are a symptom - that is something that can not be overtly observed by someone else rather a sensation that a patient reports. As others have mentioned it is a fluttering, a thud, an extra exuberant beat, pounding, irregularly beating or a whole variety of other sensations that a patient will subjectively report regarding their heart. Palpitations as mentioned above are a symptom and therefore do not mean anything until it is documented what might be causing them. It is sort of like having a patient come in and say they have arm pain. Think of all of the things that might cause arm pain - its a long list for sure. The type of palpitations you are referring to are called PAC's (premature atrial contractions). They are very much influenced by worry, lack of sleep, stressful circumstances, too much caffeine, etc. Often they resolve by simply reversing the above. Nonetheless, if your palpitations are associated with other symptoms - like shortness of breath, dizziness, weakness, sweating, and chest pain, then you should seek medical care. If on the other hand you are having a few flutterings under especially stressful circumstances with no other symptoms - they almost certainly will resolve without intervention and are harmless. It is always good practice to seek a professional opinion if in doubt. Good luck.