Most people find that an outline is good place to start writing. The outline, like a map, tells how you will arrive at your destination, the completed report. The general rule is to use the past tense to describe events that occurred at a point in time prior to the writing of the report. The present tense is used to refer to assertions that continue to be true at the time the report is written. After you have edited and revised your first draft, give it to someone else, such as your advisor, for comments and criticism.
Some advisors prefer to have students turn in a sections at a time rather than the completed report.
If possible, solicit advice from other people. Expect your report to go through at least three or four complete revisions. You will increase the quality and effectiveness of your writing if you let time elapse between revisions. During the revision process, try to cut out wordiness. Minimize the clutter by eliminating adjectives and adverbs as such as possible.