There can be some basic mistakes which can be done by the student. Once the following mistakes are corrected, his/her solar cooker will start working efficiently-
1) he/she might not have painted the cooker black. Black color is the best absorber of heat, thus painting it black will give better results.
2) he/she might not have covered the solar cooker with a glass cover. This glass cover traps the heat inside the cooker thus increasing the temperature.
3) while constructing a solar cooker one must place spherical reflectors inside the cooker so that they can converge the light at specific point thus giving a better result.
4) the sides of solar cooker must be covered with some thermally insulating layer to reduce the heat loss.