In your word processor, draw up a grid with headings like Date, Aims, Resources, Activities, Homework, save the document as a template, and use that as the basis for your lesson planning in future. If you are a manager of other teachers, make the template available to them also. Using the template will help to ensure that you cover all the important points each time, and that there is a degree of consistency of approach both over time and between staff. In all cases of using IT to reduce the burden of administration, there is an initial cost of time spent setting up a system and refining it in the light of experience. But in the long run the gains are well worth that small initial investment.
People sometimes worry about computerised reports looking well, computerised.
But even if you just include pupils names, class and examination grade in the mail-merge, you will save hours. A good rule of thumb when considering improvements in any administration system, and one advocated by the DfEE, is that data should not have to be entered twice. If you think about the examples just given, the original list of pupils names had to be entered only once. Then it could be used on the classroom wall, in an electronic spreadsheet and in a report to parents. And, of course, for many other purposes that present themselves in school.