my chainringIdeally, a singlespeed should have a frame with horizontal dropouts or track-style horizontal fork ends.
With this type of frame, the chain tension is regulated by
moving the rear axle back and forth in the fork ends. If
the chain is too tight, the drive train will bind, perhaps
only at one angle of the pedals (chainwheels are not
usually perfectly concentric). It should be tight as it
can be without binding. If the chain is too loose, it can
fall off, usually at the most inconvenient possible time.
Set the rear axle so that the chain pulls taut at the
tightest part of the cranks' rotation. One at a time,
loosen up each of the stack bolts, and tighten it back
just finger tight. Spin the crank slowly and watch for the
chain to get to its tightest point. Strike the taut chain
lightly with a convenient tool to make the chain ring move
a bit on its spider. Then rotate the crank some more,
finding the new tightest spot, and repeat as necessary.
This takes a little bit of your hands learning how hard to
hit the chain, and how loose to set the stack bolts, but
it is really quite easy to learn.