Factors which we should keep in mind while choosing a source of energy are:

It should do a large amount of work per unit mass or volume - it means that the output energy must be more than the input energy. It should have high calorific value.

It should be easily accessible - the energy source should be able to provide energy over a long period of time. Example: coal and petroleum.

Should be easy to store and transport - most common sources of energy such as coal, petrol and LPG need to be transported to users from their points of production. They also need proper storage. Thus it is important to store and transport these sources safely and economically.

Safe and convenient to use - energy sources should be safe as it is used by a large number of people and should be convenient.