I currently have about 40 CD's with amounts ranging from $6,000 up to about $50,000. I probably have about $800,000 total in CD's. The rates range from about 4.35% up to 6.5%. I usually buy CD's that are no shorter than 3 years in length and will invest up to 10 years if I think the rate is really good. But in times like now where CD rates are really low, I won't buy any CD's that are longer than 12 months. In general I don't think rates stay low for very long (our current situation may prove otherwise though). The other thing is that I learned by experience and intuition what a good rate is. 10 years ago I was able to get CD's paying 8%...I condered that a good rate then. In the more recent past, I considered 5.5 - 6% to be a good interest rate. So I had to make my best guess at investment time based on current interest rates, how long I wanted to invest the money.
As far as getting a ladder going, that's probably the hardest part....but in general if I was to start a ladder from scratch, I would probably take a portion of my investment money and buy 5 CD's (1yr, 2 yr, 3 yr, 4 yr and 5 yr). In 6 months or so, I might do that again with another portion of my savings (buy 5 more CD's). So in 6 months I would have 10 CD's set up and they would be coming due every 6 months after that. When they came due, if I thought the interest rates were good, I'd re-invest them for another 5 years (or longer). If interest rates weren't good, I might reinvest them for just a year....so that if interest rates increase during the next year, I could take advantage of that a year from now. The part of re-investing is always a judgement call on my part.
NOTE: My CD investments made up about 65% of my total investments up until the recent market crash....now they make up about 75%. I know many people here worry about inflation eating away the value of CD's, but I found that if I invested more of my money in the stock market, I was a nervous wreck much of the time. For me, I need to know that if the market crashes or goes in a prolonged downturn that I can still continue with my early retirement.