Retirement: 24 Things To Do Before You Retire - Retirement Planning Key Steps to Take Before You Stop Working
I found this list to be pretty complete. Pretty easy to watch too.
I can't say I did all these things. You start planning for retirement with a simple thought. I fell into doing many of these things by accident. I didn't put together a real retirement budget, nor did I test drive it before I stopped working. I did assume I'd live on a reduced percentage of my employed income.