Jam,
I made a simple device that allows me to measure the water depth. I generally fish two flies and always try to set my bottom dropper fly a foot off the bottom. If I measure 20' of water, I'll set my slip indicator to make my leader 19' long. If I'm not getting strikes, I adjust the indicator down to shorten my leader.
I've found that on lakes with good numbers of carryovers, this works very well. The carryovers seem to be more oriented towards the bottom keying in on chironomids and bloodworms, while the recent stockers play closer to the surface.
I hope this helps.
SF