Make sure you’ve registered any relevant social media accounts you will use or may wish to use in the future.
If it’s a localised business register it on google places for business
Make sure you have a clear understanding of backups and what would be available to you in the case of a crash.
User testing - you need people to bang on it and tell you about bugs or what is counter intuitive.
SEO is just a traffic getting method ans backlinks mainly effect your rankings - I build a website NOT for search engines but to provide a service or something of value to visitors… in other words I don’t do any onpage optimization apart from meta tag title & description on homepage. Sitemap XML file is useful if you have a very large website, GWT accounts is also useful to know if you have any serious problems on your website.
keep on updating your site regularly. At the same time, create accounts on article directories, web directories, bookmarking sites, social networks, press release sites, or even youtube. You can utilize such sites to promote your website. For me the best thing to do is to create/ad a blog and updating this everyday. Google loves relevant info.
First identify relevant Keywords related to your theme. Then using Google keyword tool find search volume of that keywords and finalize most relevant keywords. You should do this for all of your pages. Then when you write content for pages, place your keywords too in content(Not stuffing)
This is very important as i feel.