Declining A Job Offer. OK, so you know the job isn't right for you. The mode of your recent acceptance influences how you ought to communicate your rejection.
But when it comes down to it, it's all about treating the company the way you want to be treated. The mode of your recent acceptance influences how you ought to communicate your rejection. For one, they will not likely feel insulted by your action.
You want to do it in such a way that it does not prevent you from securing another - perhaps more suitable - opportunity with the company in the future.
OK, so you know the job isn't right for you.
You applied, you interviewed, you got the job — and now you want to turn it down. When They Go Low, You Go High. It will also help to make your reason(s) more acceptable to them.