Robots.txt is a text file that you place on your website (as robots.txt), that show search engines (Yahoo, Google, Bing.. etc), which pages on your website should not be crawled. It is a very import file for seo,if you do not put such a file in your website,your whole content in your website will be crawled by search engines robot. And if your robot.txt is not properly,search engines robot will fail to crawl your website or even public your privte of your website.
so robots.txt is very important for your website.
A sitemap is a separate HTML page that acts as a directory of the pages on your website. Each page listed in the site map is hyperlinked. Since search engines seem to place more weight on text contained in a bulleted or numbered list, put your links in lists.A sitemap is not only good for getting search engine spiders to follow your page links and easily crawl your entire site, it's a useful tool for your visitors because it helps them find the content page they're looking for. It may also help them click into pages they might have otherwise overlooked.
3 301 redirect
301 redirect is the most efficient and Search Engine Friendly method for webpage redirection. As we know your website link in your website or other website will be display as www.example.come or example.com
but as for google there are different with each other,so your page rank separate to www.example.come and example.com if you do not do 301 redirect job.
4 404 error ,Static url,check deadlinks for you and so on
these basic seo job is very important for your website
now i can do these job for you for just 10$
pm me if you need this kind of service, also you can get some seo suggestions(keyword Analysis key words suggestion ,web page code,
your website construction) for your website.
my pp: email@example.com
contact email firstname.lastname@example.org