Speaking about a composing process, I found two efficient ways for myself:
1. using music theory knowledge
2. using inspiration
Often I combine those two. Sometimes I rely purely on theory. Other times I let my feelings to guide me and just write what I hear inside. It depends of how much time I have for composing. By now, I like both ways and feel happy that they work yet for me.
Many years ago in school I was told by one teacher that the perfect situations is when theory becomes part of your subconscious mind and you don’t need anymore to think about it, cause by then it is part of you. You just feel, what works and what doesn’t.
Theory should not destroy the music, but to help it become emotional, positive and inspiring. Always, after composing a piece mostly based on music theory I test it for the presence of feelings and emotions, to make them as clear as possible.