Once confidence is acquired in your casting, you should attempt to fish teams of flies. The benefits are:
Greater water area covered.
Different flies can be offered on the same cast.
Flies can be offered at different depths.
Attention can be brought to imitative flies through the use of an attracter (eg. Muddler).
One fly can be used as an anchor such as in the sacrificial lure/nymph.
I like to keep dropper lengths fairly short at around three inches - less tangles.
When a three turn water knot is tied, two possible dropper lengths are formed. The upward dropper (facing back towards the fly line) is the weaker length. The downward dropper (direction towards point fly) gives poorer presentation. Although I used to use the upward dropper, you cannot do so when using copolymer, double-strength or fluorocarbon tippet material - it is far too weak. You must use the down-facing length.
Make sure that the distance between the point fly and the middle dropper is greater than that between the middle and the top droppers - otherwise all you will be doing is casting tangles and attempting to lasso the fish.
Droppers can actually assist in leader turn-over. Put bushier, more wind-resistant flies on the top dropper and heavier flies on the point. Note: some flies have a tendency to spin when cast, typical examples being floating fry and suspender buzzer. Always fish these patterns on the point.
In assisting with turn over - especially into the wind - it can be beneficial to control the shoot. Instead of dumping the line with the left hand, feed it through your fingers and slow it down as the leader is turning over. Some distance is sacrificed to the advantage of presentation. When using shooting heads you must do this as standard.