I got a heart rate monitor for my birthday this year, but have not used it enough yet to know what to do with it. I went through the book that came with it and set the maximum heart rate, etc. (Yes, I determined my maximum heart rate through exercise, not by substrating my age from 220.)
Today the sidewalks were pretty clear, so I was able to walk faster than I could yesterday and my heart rate did get up into the 140s. I'll have to do more reading to determine what that means and how to set goals.
I'm sure in no time I will be using it regularly in both training and race situations.