What are the key areas to think about when composing?

Here are some of the key areas:

1)Timbres - using interesting timbres within an ensemble. For example, pizzicato on the violin

2)Textures - what different tectures can you achieve within the ensemble? For example, homophony, polyphony and canon

3)Harmony - don't be stagnant. Move to another key within your composition

4)Melody - Create a motif and develop it through techniques such as: sequence, fragmenting, transposing, inverting and passing it through different instruments