We have technical writers who work in conjunction with developers to author the documentation. I don't know what tool they use. However, since you say you want to get better at writing docs, let me offer some perspectives based on a user of documentation.

1) Write to all of your target audience. For example if your product is targeted at both technical and non-technical people, then write the documentation in such a way that non-technical folks can understand it. Don't just write for the technical people.

2) If possible, write documentation around several 'how do I do XYZ task'? My experience has been that people tend to turn to documentation when they want to execute a specific task and they tend to search for those phrases

3) As much as is possible, include examples. This tends to remove ambiguities.