I haven't found mine yet but others have described a warm feeling washing over you, numbness on legs, hands, face/lips, ringing ears vision darkening/fading, euphoria, Shaking (there was also a person that said I watched the devil burning me with fire)....etc
The main indicator is when you find your sweet spot you will loose consciousness in less than 10secs. If you stay in that position for minutes without any thing happening u have not found it.