Composing music for a film is a task that is often crucial to the films succes.
Tips to creating the best music for film possible are
Get to know the film/scene. It is important to really get involved in the project you are composing music for. Watching it on silent over and over again may become tedious but it will give you a feel for the clip. Taking notes on how the scene is formed, shot lengths, cuts dialog timings are all important things you will need to consider and build the music around.

Experiment with instrument choices. Some of the best music in film can come from instrements you may have never heard of before. Being original with instrument choice will not only make you're work stand out from other producers but it can also offer a real unique feel to the film because of the rarity of how a peice is composed the viewer will remember the music a lot more. The more original the music is the more the viewer will relate that piece to music to that film

Understanding and sticking to the rhythm of the film. Recognizing whether  the film has a fast/ slow beat tempo will allow for you to compose in conjunction with the way it is filmed. Giving the film a seamless and natural feel.

Complete more than one piece of music. if it is possible making a couple different sound tracks would be recommended because watching the film with one soundtrack and then trying it with the other will allow you to see the differences, what parts worked where and what kind of atmosphere really suits the clip. Allowing you to pull out different parts of each to create the best piece you can to match the film

Keep the music in context. Having music in a film that is actually suited to the time period, location or characters. For example using a chinese style peice for a scene set in china. It offers an authenticity to the piece and helps the viewer understand the kind of cultural setting the film is in. It is also useful so it is clear wear the place is set and to make destinctions between other shots set in different locations

To make the music for the dark night Hans Zimmer had to make music to suit the characters and the atmosphere of different shots. He complied many different peices. This is so he can listen to them, show them to Christopher Nolen so he could compare and contrast them and help come up with the perfect piece