The formula consist of a combination of "Food access + Water Temp+ Oxygen + safety". If any of these is missing or of a lesser value then ideal, it would reduce the odds of the fish being there, unless options are slighted. Examples might be as follows:
---- water temp in excess of 65 degree will do if the max depth of water is 15 feet.
---- 30' of water along a east lake side bluff, may provide enough oxygen with a breeze out of the west, churning the water, causing a bit wave action and down current. Add a shelf of 5' water along the shore line that that allows plant growth, and you increase food and cover, plus escape to deeper water, and you increase odds of them being there.
Bottom line.... learn your lake, study maps and water features, even keep notes that allow you to compare to similar combinations week to week, lake to lake! My first time on a new lake and there are "patterns combinations" that I can assess quickly that allow me to "guess better" until I have proven out parts of the lake.
Example:
Shoreline rip-rap, with waves blowing in, later in the day, looking for 10-12 feet of water, if my time is otherwise limited. Will start out fishing a bit cross wind of my anchored kayak, drop bait (fly) 10' below float, and allow it to drift towards the shore. Will shorten up depth of bait by 6" after every 3-4 fish-less drifts, letting the rig drift more into the rip-rap.
No rip-rap? Hmmmm pick a shore line point, having similar wind-age and set out to drift bait (fly) the same way so as to swing in drift, across the point, starting with say, bait 8' below float, fished in 10 of water .
Or try the same idea and rig, drifting in towards the outer face of a weed bed such as coon tail or even lily pads. if you're not finding the fish, re-position closer to the weed bed and dip a bait (fly) down through the outer edges of the weeds.
Crazy thing about it.... 25 of us will likely seek out 20 different combinations or variations, given a new lake with no info from a local, to get us started. Add electronics to the madness and its a whole new "guessing game".