This trick requires that your character has 100% or more Invisibility or 
Chameleon. This is done by either
enchanting a number of armor, rings, or amulets, or you can enter an 
Oblivion Gate and keep reloading the
game until you find the Sigil Stone that offers Silence and Chameleon. After 
you get that stone, use the
"Duplicate items" trick to instantly enchant your items without having to 
find Soul Gems and Souls. Once
you have Invisibility, go up to a guard and start beating him up using 
hand-to-hand combat. When he dies,
more guards will keep spawning. You can just keep beating on them. You can 
also find a character that is
marked with a crown that will not die, and only becomes unconscious. Because 
they do not see you, it is
not bad. Also, they never die, so you can endlessly beat on them until you 
master Hand-To-Hand. Your
skill increases about every 20 seconds or more, depending on how high your 
skill level already is.