SAFETY: If using jars with lids to cook food. Do not tighten them all of the way, or make a small hole in the lid. Steam needs to be able to leave the cooking container. Do not put frozen food in hot evacuated/vacuum tube cooker. The thermal difference when you add the food may break the glass.)
Increase the temperature by directing the solar cooker at the sun more often (i.e. every 30 minutes instead of every hour). Increase the surface area of the reflectors (i.e. use bigger reflectors). Add insulation. Adjust the reflectors so the light bounces towards the food. Use shinier reflectors (i.e. Use the shiny side of aluminum foil instead of the duller side.) Clean the glaze to allow more light to shine through.
Decrease the temperature by doing the opposite of the above. Move the solar cooker so that it does not line up with the sun or make a small opening in the glaze to allow some heat to escape. Put the cooker in part shade.
Make the food cook faster by using multiple smaller pots than one big pot. Cut food into smaller pieces to cook it faster and more evenly. Use shallow cooking containers instead of deep cooking containers.
The best time to cook is around 10am - 3pm.
Preheat your cooker (UNLESS it is a vacuum tube cooker). It helps you judge the time better if you are following a recipe and is safer food handling for more perishable foods like fish.
Cook more food by using a bigger solar cooker.