I think Byron is on the mark with consulting a hatch chart for your area. For the months off the chart (Nov-Mar), I think PlanetTrouts suggestions of midges, scuds, and sowbugs are on the mark. A small (#16-1, dark Pheasant Tail or similar to imitate Blue Wing Olive nymphs and a cased (or peeking) caddis imitation also work well for me during the off months. I fish for trout on small spring creeks at a similar latitude here in SE MN and that's what works for me.