So sorry, the question is too generic to really answer specifically.
Ranking in Google Local is like a giant extremely complex PUZZLE. There are in my estimation over 300 ranking factors in the blended algo.
Some of the puzzle pieces are on the G+ Local Page, some are on other sites across the net, some are on the web site. But some puzzle pieces are ones an SEO can't control which include things like how many reviews, how close to city center office is, how old business is and how old domain is.
To a large degree whoever has the most important puzzle pieces, all lined up in the right places WINS and gets to rank on top in Google.
So lots of it depends on what puzzle pieces the client already has, so we can see which pieces are missing AND it also depends on how competitive the KWs are and what pieces the competition has. Also depends what keyword, city.
There is no generic advice or secret tip we can give for how to move someone from #8 to #4.
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