Try the many google keyword tools. Including: traffic estimator and adwords keyword tool. Also try checking out some of your competitors keywords with google's search based keyword tool. Those will give you some idea of the value of your keywords and help you add to the list.
thats a good idea mkroon but hey the keywords i came across are like have a heavy competition on them i.e printers>>> and it really describes what i have to offer...how shall i go about it? should i use less competitive/less searched terms...or should i go with it and use extensive inbound linking for it?