Once you've accepted the offer with your new employer and set the start date, obviously the next step is to let your current employer know you'll be leaving. Write a brief letter of resignation (the operative word there is "brief").
If you feel a need out of loyalty or guilt to write anything more than a few short sentences, curb it. The only information your letter needs to contain are the following two (possibly three) items:
-- that you are leaving your current company
-- what your last date of employment will be, and
-- if you feel comfortable adding a sentence or two about how you enjoyed working for your current company, and you appreciate the opportunity to have been a part of the organization, tack that on
It should NOT include:
-- why you are leaving
-- where you are going
-- what you will be doing in your new position
-- how much you will be making when you get there
-- how bad you feel about leaving (or conversely, how glad you are to be going!)
Make an appointment with your boss and hand deliver the letter. Tell him verbally the same words that your letter says, because the face-to-face is courteous and professional, while the letter is a formality for record of your employment. And be prepared for one of three things to happen.
Either your boss will professionally acknowledge your resignation, say how sorry he is to have you go, and shake your hand, or he will become very silent - just before he asks you what it would take to keep you. Or quite possibly, he'll do the former, and you'll be asked to another meeting later so that he can find out what it will take to keep you.
If your company is truly professional, you'll resign, shake hands, and that will be that. But it doesn't always go down that way, which takes us into the second way to resign, which actually is in danger of not being a resignation at all. It only starts out that way.
The first thing you need to know is that a counter offer is NOT - IS NOT - a sincere and genuine statement of their desire to keep you around for as long as you might decide to stay should you change your mind and accept their counter offer.
What you've just done by resigning is put the company at a disadvantage. You are creating an opening within the company, and you've left your company at a loss. By resigning, you've basically said, "I'm not interested in this company any more." You've caused your loyalty to be questioned. You are in control, and they are not.
If your boss invites you in for a concerned chat, you're better off sounding like a broken record - repeating your "thank you" and "my last day is..." than you are involving yourself in what appears to be a caring conversation about your ensuing future.
It doesn't matter what you want or what you ask for, because they'll give it to you - in one form or another - or possibly offer you something tasty before you even speak up. After they've lulled and flattered you into submission, and as you walk out the door smiling, they're calling the newspaper or a recruiter and ordering up a confidential replacement.
In 25 years of recruiting - my firm, and working with other firms - I have never, ever, ever seen an accepted counter offer work in favor of the individual.
Don't, for a minute, think I am being overly dramatic. A counter offer is a complete and 100% appeal to your ego and an attempt to push your guilt button. It's unprofessional of your company to attempt it, and it's unprofessional (and ill conceived) of you to take it.
It might be a month, or six months, but eventually, your next departure from the company will be on their terms.