Along with rec.gardens.orchids (you can see the fine help posted
already) you can use a Search engine like GOOGLE. Try "Oncidiums 101".
That gave me many sites discussing Onc. care. The information will at
first seem overwhelming, scattered, different strokes from different
folks, but after researching it a bit things will start to fall into
place.
Now for my two cents; Use the south window but place it to get only
the morning sun and bright shade in the afternoon, possibly south side
of a larger plant to filter the afternoon sun. Use expanded clay and
repot in a SemiHydro type arrangement ( Google again). Feed with a weak
solution bi-weekly. Flush with water weekly ( Run 2 quarts of water
thru a one quart pot). The leaves should go to a light green with a
tinge of yellow (dark green indicates too much light). Relax. ;-)) For
me half the fun is the research and groups.
Joe T
Baytown, Texas