As this is my first daily post for tips on composing (and more importantly, in regards to fantasy music), I wanted to relay a suggestion I received when I was starting out.
It is called the Rule of Threes. Basically, with orchestral writing, you want no more than three primary things happening. When you add a fourth, it gets too difficult to follow with your listeners.
Let me give you an example. When writing a soaring adventure piece, here are three components you might use: Some great staccato strings or runs in the background, a grand melody/theme by the french horns and trumpets, then a lower harmony by trombones, tuba, and bass.
Another example. When writing a romantic piece, you can have the strings playing a romantic melody, the horns playing a counter melody, and the harmony playing on the low end to give it depth and color.
Those all have three main components. If you add a strong fourth component, it gets too complicated to focus and listen to. Of course, there are exceptions to this, but starting out, it's good to focus on the Rule of Threes.
One side note. Some percussion hits, a nice woodwind scale run, or some nice glockenspiel notes here and there do not count as a primary component. Think of those as garnishes on the main dish to give it more color.
Anyway, hope this helps some newcomers and happy composing!