Well the very basics step woud be to do on page SEO and implement what we call best practice ,on page SEO shoud be first step because off page SEO results depend from it.
When it comes on page SEO you can split tasks in few groups:
1.Put optimized and unique content on your site,optimized mean that it is keyword optimized and with good Text/HTML ratio
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2.properly marked and tagged content-this mean you must use properly tag for every title,subtitle,text area.....because from that depends how and which content will shows up in search engines .Main keywords you shoud put in titles/subtitles and tag it with H1-H6 tags.
3.ALT tags(attributes) for video and imsges is must have since it is only way search engines can index it.
4.Implementing rich snippets is also good thing to do
5.From recently google rank higher sites that implement https protocol so SSL is also must have
6.Also like https protocol mobile frendly sites rank higer,offcourse it does not mean you will rank better than any non mobile frendly or non https site.
7.google also look for Google+ publisher tag so make sure you add your site in Google+ page setings and also put Google+ publisher tag on web site
8.Make sure you have updated Robots.txt and sitemap files
9.Pick only www or non www variant and redirect to it and also forward server IP to your site if using dedicated IP ,since if you are using dedicated IP and not forward it it will result with double content.(for more google "IP Canonicalization ")
There is more things to do like language markup,fast server,do not use underscores when naming files insted use hypens,check often for broken links...etc
These are very basics and there is a lot more,when it comes offline SEO there is a lot of you can do and everyone has own way to do but keep in mind that search engines use much powerfull algorithms and do research before start using any techniques.