1. Don’t use excessive amounts of bleach and disinfectant, these will both upset the balance of the septic tank. (I presume this is what you mean when you say cesspit.)
2. Don’t dispose of any non-soluble items down the loo such as sanitary towels etc.
3. The number of people in your household will determine the frequency of emptying the septic tank/cesspit. Usually once per year, but can’t be dogmatic on this. Don’t let it get to the state where it pongs or the overflow is running black – both are bad news!