trixel

If you know this already, apologies.

First and preferable, peel and chop into chunks about 2" long. Roast - either with other vegetables (worth dribbling a little oil on them, if you do this), or in the same tin as your meat, if you eat meat; they pick up the meat juices, which is good.
40 to 60 minutes; gas mark 5 or so.

Second, peel and chunk. Put in water salted to taste, and boil till soft-ish; seven to ten minutes, IME .

Third, as second, except boil for a couple more minutes, and mash with butter. (This works well with added carrots.)

Fourth, chop small and eat raw. Not to everyone's taste, but worth a go (especially when you have a bit too much for one of the other methods ).