Continuing from my post of Leaving vs. Staying Back, here is what I learnt about the "right" process to do when rejecting a job offer.
If you have been offered a job by another company, you would then get an offer letter which you have to sign within a stated time period, usually within a week. Signing on that letter means that you have agreed to join them.
Usually candidates would wait for the offer letter before tendering in their resignation. With the letter, they have a firm document in hand - they have a job in another company. They would then let their current employer know that they are planning to resign and submit the resignation letter. During this period, if the company wants to retain the employee, negotiations would take place, and then the candidate would make the final decision.
The unspoken ethics about this procedure is not to sign on the offer letter first before letting your current employer know of your intention to resign. That shows your company that you would like to give them a chance to retain you. If you have already signed on that letter, then what can the company do? (Unless your company is really crappy and you wouldn't think twice about leaving). However, nowadays, many younger generation employees think nothing about putting their signature down on that letter. They think they can still reject the new company if things work out alright at the old company - as if the signature carries no weight at all.
In my experience, the candidate confirmed joining my company and signed on the letter, and then gave 1 month's notice to his old company. During that period, his company decided to woo him back and succeeded. It took the candidate a total of 2.5 weeks after signing the offer letter to tell me that he won't be joining us after all. Imagine my frustration - I lost 2.5 weeks because during the time I thought he accepted, I stopped interviewing others. I also lost my 2nd choice because that candidate decided to accept another job after hearing that we didn't offer her the job. The results were devastating to me. I had to start interviewing all over again and it was already so late - my project timelines were thrown off course.
My boss always said it is ok to reject a company's offer on 2 conditions: 1. You have not signed on the offer letter and 2. You don't take too long to tell them. That's because if you are good, your company will fight to keep you. So if you reject an offer, the other company would understand that you really are that good. But be considerate, let them know early so that they, too, can move on. And have integrity, your signature should mean that you intend to keep your end of the bargain. The CEO's signature on the offer letter guarantees that you have a job, so why shouldn't your signature guarantee something to them?