I trade them pretty much as I mentioned a few pages back. I wait for price to hit a level I have interest in and believe to be of significant value.
I then wait to see what the reaction to that level is and make a decision to go long or short. Depending on the timeframe I am looking at for that particular instrument, I may want a confirmation of a day or several days, or maybe just 15-60 minutes if I am playing a bounce back to a previous level.
I don't really think there is any magic to it and there are definitely not any guarantees, and you are right, just because you have identified a level that has a high probablility of being hit doesnt mean you have mastered anything.
But lets say for example one is watching what is going on with ES right now ... I would be looking at (for starters) are we seeing a significant increase in volume as we approach this level, is NQ / YM approaching significant levels as well at about the same time? How are they are reacting to those levels ... is it in sync with ES behavior, etc.
Those are just a few things I would be interested in seeing before making a decision.