You may want to do some mastering on the final music like control the dynamics and a little EQ. But not in the same way you would master for a CD. Loudness wars do not work here. The broadcast standard for TV etc is something like an average level of -20 dB rms.
If you give them a loud master they will turn it right down when they are putting it back with the original video. But if you keep the average level down then they can leave it alone and your music will breathe and sound better. Might be good to ask them what sort of levels they are expecting.
Check the mix coming through a typical TV audio speaker as well to get an idea how it will end up.
Create the session and produce the final cue at 48 kHz as mentioned above. (Although in many cases if you import a 44.1K cue into a video production the video software will often convert the sample rate on the way in but if you are at 48K already it is one less thing to do.) It will import faster.
Put a sharp blip noise 2 seconds before the first frame of vision so they know where to line it up.
(especially if the music has a slow start) Look for the emotion in the vision and the feeling the vision is giving you then compose the music to suit that! If it is your first time at this you will almost get it wrong the first time. It takes many years of experience to craete a very correct cue for any vision first up. Don't take it personally when they tell you it sucks. Move on the way Roger Federer does when he looses a point. Just try a different approach. Remember failing faster and failing more often is the best thing that can happen to you!