h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Read your contract and know your statutory rights, and make sure that you let them know long before you leave what you'll be expecting in terms of a settlement, i.e., in your closing salary packet. Be sure you're getting whatever notice is due to you.

You'll need to calculate how much leave (and other benefits like flights, etc.) they owe you and let them know in advance so that you can agree. You don't want to be arguing about it after you've gone.

As someone that it has happened to, I can offer the following:

If you are in a Trade union( I was thank God), get them involved as soon as possible. If you're not in a union, Join One NOW.

NEVER accept the first offer that you are given!
My Union managed to up my final offer by about a third.

Don't let them railroad you. Own the timetable. If they desperately need to get rid of you they will up the money to get it through.

BE Professional! Work your notice with dignity. Don't give them an excuse to get rid of you on their terms.

This is all fine if you've been there forever and they owe you a severance package. If not, its done like this (at least in Canada):

You carry on with your day same as always, although in one case I know of, the girl's computer password didn't work when she went in in the morning. Sometime around mid-afternoon, you get asked to go to Human Resources, and they tell you you're laid off effective immediately. They have a choice, 2 weeks notice, or 2 weeks pay. They usually opt for 2 weeks pay. They want you to clean out your desk immediately and leave. Depending on department, position, and your attitude, you may be escorted.

Best advice:

Go back to your desk, immediately log out of the computer, preferably with someone you trust watching. Clean out your desk. Take only what belongs to you. Leave stationery, pens, paper clips, etc. as they are. Turn over any unfinished business to a trusted colleague, with instructions for its completion. Say your good-byes, and leave quietly. A nasty trick, which I did myself, is to go up to your supervisor, and that's who decided you were redundant, and shake their hand. Tell them its been a pleasure working for them and wish them, and the department well. Guaranteed to make them feel terrible! Maintain your dignity and professionalism right to the end. If you want to howl, scream, swear, call the company and management names, save it till you're at home.

My last redundancy I was offered pay in lieu of notice, which I accepted & offered to work the rest of the day "to tie up a few outstanding projects". Instead I used the time to clear any personal stuff off my PC, say goodbye to friends etc. As for turning over unfinished business to a trusted colleague, let them figure that out for themselves. Redundancy means "we do not require your services any more". Take that literally.

ps. If you've been paying any attention during your time at the company, you will know where a few bodies are buried. The company auditors always like to know about these things...