Every writing manual tells you to be clear. But very few show you how.
One that does is Style: Lessons in Clarity and Grace, by the late Joseph M. Williams and Joseph Bizup.
According to Williams and Bizup, the first two principles of writing in a clear style are as follows: make your grammatical subjects the main "characters" of your "story"; and express key actions in verbs.
To see what they mean, consider these two sentences, each of which says the same thing:
The assessment of the budget on the part of the board led to the recommendation that better management of travel costs was a need.
The board assessed the budget and recommended that we better manage travel costs.
Why is the first version harder to read? For one, the subjects--assessment and management--are not the main characters. Nor do the verbs, led and was, express what's really going on in the sentence.
Look now at the second version. We see that the grammatical subjects, board and we, correspond to the two characters in the story. And the verbs--assessed, recommended, and manage--represent the key actions.
Match characters with subjects, and key actions with verbs, and you will be on your way to writing in a clear style.