how to play spy: a guide by han(d)s

step 1: go invisible
step 2: get behind medic
step 3: stab said medic
step 4: (optional) stab other guys

repeat for remainder of round

Romago asked: What do I do when the round ends?

Answer: What a great question, and I'm sorry i forgot to mention this in the main guide. Preferably you want to taunt on the round end but if you're unable to you can always say something witty in the all-chat, like "u r bad" or "lol u suck".