Hey Janet,
this thread might help.
http://forums.taxi.com/topic130947.html
Its a deep subject, and its not easy at first. Some of it is just your approach, some of it is maximizing the effect of your orchestral sounds, and some of it is the quality of the orchestral packages you use (unfortunately).
There are a lot of packages out there that are setup to sound pretty convincing out of the box.
To make orchestral samples work, you have to make three things happen - good composition and orchestration (i.e. know how to write for strings so they don't sound like they are played on a piano), good choices with string sounds and articulations, and programming them and mixing them in a believable fashion.
some things that I would focus on:
1) find an orchestral seating chart - that shows where the violins 1 and 2, the violas, the cello and the contrabass are on stage. Its not an absolute rule, but most people expect to hear the sections coming from that part of the stage. Pan the sections to those locations.
2) figure out how to use your keyboard controller to get some life into those sustained notes. Its going to be CC1 (mod wheel), CC11 (expression pedal) which are the things that will help those strings rise and fall in volume and intensity. basically: loud notes are cutting and bright, quiet notes don't have the same bite.
3) listen to some string orchestra recordings, and some film music with string orchestra and try to match the ambience (i.e. reverb) that the sections have. Most of the time to my ear, strings recorded in a hall are more lush and reverb-y than what you have.
good luck!
