Any time you change course or speed, you should record it in the log, and you should log your position every time and place you can absolutely be sure of it, and often enough between those certainties to be useful. In practice, you can get away with recording only the average or general movement in some cases, but you have to know what to do in case the details become suddenly important. As for the chart, dirty it up good. Draw a line from your previous known position to get your actual course since then. Draw a line in the direction you think you're going.
Some people write the reciprocal on the other side of the line, which is also useful.
It sometimes helps to write the time you are at a given point, as well. Other things that need to be put on the chart are described below. In order to navigate, you must know how fast you are going. As there are no knotmeters on club boats, this requires using the traditional techniques. As you become accustomed to sailing, you will find that you will acquire the ability to judge boat speed by eye - practice this whenever you can, whoever is navigating.