Much like pulling your finger with different results!
I like to pull my indicator and see what I got!.. Problem here is you cant get away with it on every drift, and practice is what it takes to hook up regularly on any drift.
In the photo above I was fishing a single fly with an 8.5ft leader tapered to 6x, and nothing else on the line.
One must find and use a sixth since so to speak. Granted, now and then your line will be tight enough that a fish will grab your fly and feel you, then set its self, but where the true art of this lies, is when your own being is willing to play the game.
Setting the hook with your mind first and your body following, is a level of satisfaction that is somewhat addicting.
The best place to try this is on your favorite hole... The one that you know the drift of no matter what the flows... A run that is flowing slightly away from you will prove to be the best place to learn as your fly will be trying to reach the surface here when you have an indicator, but removing it will let the fly go down deeper while keeping enough contact between you and your fly to detect a strike...
Just as I released the big brown I snapped a shot of the run...
Notice that the water is moving slightly toward the far bank and shelfing off mid river... Essentially this keeps the line tight for you, while wiggling in some mends to achieve depth.
Start by shorting up your leader some and watching only the spot where your leader meets the fly line. Each time you cast, this spot in your line will take the same shape and look pretty much the same after your nymph hits the bottom. If that shape changes then it can only be two things, a fish or the bottom... And as we all know its not usually the bottom!