I know you should separate all keywords with commas, but should you put phrases in quotation marks?

i.e. alley, alleyway, �back alley�, bin, bins, city, dirty, �run down�, dumpster, dumpsters, garbage, gutter, lane, polluted, road, street, urban, industrial, industry, construction

I've noticed some sites take them and some sites break up the quoted parts.  Is there one system that works for all sites?  Are the commas enough?