How to select for temperature conditional mutants among a population of a particular organism?

It depends on the temperature and the organism. uming it is a micro-organism, if the organisms thrive at a particular temperature then use an incubator for warm temperatures and a fridge for cold temperatures. Set the container at the optimum temperature for the conditional mutant you are trying to select for. The largest colonies (the most successful growth) will be the conditional mutants. You can pick these and grow from here.