I have to agree that few search engines use keywords any more. However I have seen few websites that didn't incorporate them into their meta tags. If you chose to use keywords on your site you want to delineate them with a comma. As an example here are the keywords and how they are formatted on Lawnsite.
<meta name="keywords" content=" Meta-Tag Keywords, dixie chopper,exmark,toro,lawnsite,lawn care business,lawn mowing business,lawn business forum,aerator,commercial mowers,lawn mowing,shindaiwa,gator blades,irrigation,scag mowers,sulky,walk behind mowers,landscaping,lawn maintenance,walker mowers" />