The biggest factor facing all UAV operations is weather. Stay on top of the long and short range forecasts and keep your client in the loop and reschedule accordingly. This includes sunrise and sunset times as well. You don’t want to show up an hour late and miss the best light of the day.
There are a number of online weather resources available, pick a few and get familiar to how their modelling matches reality and compare multiple to get a good overall sense of what to expect as it can vary between sources. We use Windfinder as one of our main sources and find the hourly wind predictions fairly accurate for our area, but there are many available to pick from.
For sunset/sunrise times and sun angles there are numerous mobile apps such as Sun Seeker:3D that will show you the angle of sun throughout the day to help you maximize each angle for a given location.
A good piece of equipment to have in the field kit is an anemometer. This allows you to quick check wind speed to ensure your within the safe limits of your aircraft. There are a number of handheld versions available, including smartphone add-on devices such as the Vaavud Wind Meter.
Another factor to keep in mind in regards to LIPO batteries is the air temperature. On colder days the effective “C” rating of the battery will be lower and thus you may see reduced flight times. Be sure to not push the limits on these days by solely relying on flight time alone as the voltage may drop faster than expected in colder temps.
Be sure to always account for alternate weather dates for reshoots in your planning so both you and the client can leave schedules open if needed to makeup for lost days.