Have a look at this shortened clip from my DVD (compression for web use isn't brilliant, but you get the idea).
3 most important things are:
- Location of the fish within the river (reading the water, which the DVD covers in more detail)
- Having your point fly hit depth (i.e. within inches of the stream bed) in only a few seconds (less than 5)
- "Contact" with your point fly to detect takes
You must always have the rod tip and tip of fly line travelling downstream ahead of the point fly, and the leader must be as straight as possible between the tip of the flyline and the point fly (no slack)
If the point fly (or any other fly) is travelling downstream ahead of the fly line - you have no bite indication at all and grayling quickly blow out flies from their mouths once they realise they are not actually food. (you will hardly ever feel a take - it is all visual and all subtle)
Use level (not tapered) monofilament from the tip of the flyline and make the overall leader length just a little less than the length of the rod.
In VERY slow flat water - it can be useful to use a floating indicator (yarn, very buoyant fly or even an out and out Fish Pimp style bung). However, most of the time, just a brightly coloured section of braid attached to the permanent loop of your flyline is what is required.
The default setting is to always keep this braid just half an inch or so ABOVE the surface of the water (not touching - so that only monofilament is in contact with the water)
Where you cannot reach far enough to do this, if the water is steady paced enough (if too fast it will whip the flies out of the feeding zone too quickly and too shallow) you can cast a little line - but hold the rod tip high and only lay the last 18" to 36" of flyline on the surface. You must still have a perfect contact between the tip of the flyline and the point fly when you do this (the first part of the czech nymphing section of the DVD shows this approach - it is more difficult than the default approach of holding all the line off the water and tracking under the rod tip).