Got to the link I provided, then click on "Search Term Suggestion Tool". A small window pops up, you type in your domain keyword, press enter, and you get overture counts for several similar terms.
For example, if your domain is SellCandles.com, then "sell candles" is the keyword. In the OVT tool, "sell candles" has no hits, but "sell candle" has 243.
Clearer?
- Apollo