When you put categories on Google local business thingie I think that's what determines keywords that you will show for, also your title tag in local business center and the description there. So far I haven't noticed the keywords and description or title of your actual website affecting google maps. Not 100%, but that's what I noticed so far.
yeah i just can't figure it out since the map has to be local i put in diamond exchange as a category now my site is a diamond exchange in boston so i thought it would appear for a search boston diamond exchange