Hardcore drying involves complex mathematical calculations. But, the following are just simple tips. Do not worry!
1) Surface area matters. The more surface area the faster the drying time will be. Some practices to increase surface area are slicing, chopping and pulverizing. That is if particle size reduction is allowed or is the normal product requirement.
2) Heat. Higher temperature drives moisture away faster. It is but normal to use the maximum heat possible that is not detrimental to product quality. E.g. If mango slices turns brown at 90C, then the machine operator should try lowering the temperature as to maintain the yellow color.
3) Layering. I mean how the commodity is arrange on trays. Crushed ginger when arranged on trays 10 mm thick will dry faster than 20 mm thick arrangement. A simple theory but we often put thicker layers to load more at time thinking work could be faster.
4) Air flow. If the commodity being dried is in enclosed system or a system with a very minimal air exhaust, the result is a slow drying when the moist in air became saturated. There must be an efficient way to take-in dry air and expel out moist air. Note that you can dry any commodity by using moving air alone. The best scenario is clipping your wet socks on rotating fan.
5) Rest. Surface moisture could be removed easily with combination of heat and good airflow. However, the inner moisture is not. Especially true for grain commodities. A good trick here is turning off the drying machine after an hour or two. Allowing the inner moisture to travel to surface. Then continuing the drying process. This may not result in faster drying time but to a more cost effecting drying.
6) Heat source. They said far infrared heat is more effective than convection heating. This heat source acts on food commodity directly. When struck with infrared wave, the molecules rotate causing rapid heat build up and driving away of moisture. The only major drawback is the high energy cost of powering up the infrared heat source. The common around is ceramic type.