[torero]

You picked the right spot to set your stop, below support (assuming you were long above it). But you should put the stop as soon as you make your entry. You can always cancel and move it if you think it's justified. As MrPaul mentioned, some freaky incident like internet connectivity or power outage in one minute can be a hazard to your account. It's a lesson easy to solve but hard to execute until a big loss forces you to change your habit.

As for where to place stops, that depends on your trading strategy and research. It's difficult to do but once you found a consistent spot, taking stops if a lifesaver. I usually place stop the low of 2 bars ago or the last pivot low for long. There are tons of books on explaining on how to place stops. But it must match your strategy and trading style.