I usually start with a battery check and zero adjustment on the meter (usually a small scew marked as such on the back of the instrument). Then a test on a landscape with normal ligt (a cloudy day is even better) and a check with a camera with a normal lens (50 mm on a film camera) will do the job. Try to point away from the sun, a big grey surface is perfect. Hold meter and camera in the same direction. Std meter function on lightmeter, no bulb on the cell. Std meter function on camera, no spot metering.
In such a test, a meter on a camera or a lightmeter can differ 1 stop, no 2 stops.
FYI, You can always download the instruction book for your meter from the Gossen site (Germany). The also keep the instruction books for old meters availiable. Nice site.
Do the zero adjustment first, preferably with the battery removed from the meter and the meter held so the needle is horizontal. The instruction manual will explain.