Do you trill up or down on piano?
Trills provide the flutes and other woodwinds the opportunity to add brilliance and excitement to a score. Forgive me for stating the obvious, but a trill is a rapid alternation between adjacent pitches, up either a half step or whole step from the notated pitch (never down).
What note do you start a trill on?
Trills almost always start on the note higher than the one that's written. So if you've got a C with the “tr” symbol above it, you'll almost definitely be alternating D-C, starting on D.