For my "maximum comfortable range", I typically burn from the reserve for about 15 minutes (usually in taxi/takeoff/climb), then burn the drop tank so I can drop it and get rid of its drag ASAP. This does leave me with a bit of a wobbly pudding of an aircraft trim-wise until the drop tank is gone and I start burning from the fuselage, but I figure that's the price of economy!
In an effort to not "cheat" and look at the fuel loading sheet in flight and also avoid wasting fuel by running from a non-reserve tank with a full reserve tank, I usually burn in the following pattern for maximum range:
1) Taxi, takeoff, and climb on reserve
2) 100% of drop tank, then drop it
3) 15 minutes on reserve
4) 100% of fuselage tank
5) 15 minutes on reserve
6) 50% of wing tanks
7) 100% of reserve
...then I try and be on the ground before the wing tanks run out. Something about flying on a tank with no level indicator really bugs me, especially when I'm doing something important...like landing.
Hope this helps,
Commercial Instrument Single/Multi-Engine Land. Police, Fire, & 9-1-1 Dispatcher. MAINEiac Crew Chief.