27 Jan 11 2:26 pm
We tend to look at broad match initially, then narrow down to exact because the results can be quite surprising.
Numbers depend on whether you are looking for a main keyword, or just a secondary but 3k in broad will generally equal around 1k in exact, and if you can get a top 3 ranking you can expect maybe 300 visitors a month.
Then if you rank well for that term chances are you will also rank well for a few related, bring ing ing the same again.
Repeat 10 times and you've got reasonable traffic.
PS Don't be put off going for the higher numbers of search too, if you stumble across an uncompetitive term it can be very nice ;-)