NAP acronym sands for Name Address Phone. You need to ensure that your are consistent in the way you list your Name, Address an Phone data on your site and on other citation and directory sites. Discrepancies in the way you are listed across various properties including your own site and on Google+Local, Google Maps, Yelp, and all the other directory and citation sites - can result in the Google Local engine to not give you ranking points for the local seo citations.
You can find broken internal links from within the Search Console. You need to attend to each warning appropriately telling Google that you have fixed it. Having excessive 404s will hurt your site if they are really 404s, because anyone could escalate the 404s by pointing randomly to pages that don't exist from external places, which is why this is not that big of a deal - but should be looked at.
To find keywords which generate traffic and conversions, try to use modifiers that are appropriate for your niche. If you run a business that sells on a large scale, modifiers such as the words ‘wholesaler’ or ‘retailer’ can help you find your ideal client. People looking for quality use modifiers such as ‘best’ or ‘elegant,’ while those looking for the best price use ‘cheap’ or ‘discount’ to find your product.