Glad you asked. Here are my tips to share:
1) Your light source is important. I had problems in winter and early or late during the day because of the position of the sun. Try to take your readings when the sun is reasonably high in the sky.
2) I shot the sensors on my chronograph a couple of times. Once because my scope was radically off and another time because I was firing bullets that were so unstable that they tumbled out of the barrel and went off course immediately. Avoid such headaches when dealing with new guns and loads by firing a shot at a target first.
3) Put the chronograph 15 feet away, at least. If you're shooting a magnum you don't want to be closer than that because it'll really rattle the chrono. Also, you could get erroneous velocity readings because of a shock wave if you're too close.
4) Use the chrono to check your load performance, not to try to create maximum speed loads. If a reliable manual like Speer says 2500fps and I'm getting about that with my load, then I'm happy. If my reading is significantly faster than the published velocity, then I may have a pressur problem that needs to be addressed.
5) Manuals differ. Lyman velocities are almost useless. Nosler velocities are typically overstated. Speer and Hornady are very close to what you can expect with real guns.