As is mentioned in the previous blog entry duplicate contents lead to a big downfall on SERPs. A poor link architecture does as well. Your links should establish a perfect hierarchy with prime placement. Duplicate page titles not properly written or too short will also affect your rankings.
Use the title tag to inform the visitors about the page content and the location. For location one should schema mark up. Do not stuff keywords artificially and keep the length to 75 characters with space maximum. Your title should be effective in sending the right message and fetching an impression.
Meta Descriptions though not very active in ranking are a must in all important pages. They should effectively add to the titles message and offer more details. Some add address and phone numbers to the tag as a portion is visible on the SERPs. The description should be about 250 characters along with spaces. The message should be very clear regarding the offerings and hence compel the visitor to click.
Write title & meta for all pages with right meaning and accurate description. This will also help whence Google exhibits sitelinks of your websites on the SERP. Add all meta element as relevant for example use index/follow or noindex/nofollow tag in all pages.
Analytic code missing. You will not be able to gauge the performance of your site on SERPs and analyze for future action. Google analytic code is most popular it should be added in all pages before </body> tag. Keep checking for any errors that may creep in.
Structured markup or rich snippets are required hence we will take this aspect separately. The rich snippets carry ratings and reviews which can be effective as conversion tool for impressions.
Do you forget to check for broken links and old unused codes? One should regularly check for these since in case of former site navigation is affected while the latter will slow down page download.
Absence of site maps. Both html and XML site maps are needed. The former is for visitors and the latter is for search engines.