What the heck does “keyword” mean? “Keyword” is not a technique, it’s a buzzword used by snake-oil salesman to justify charging you lots of money.
How about
5. Improve quality of HTML to make the site accessible and usable, with useful <title> and <meta> description.
keyword is not a technique but keywords are to be optimized using seo techniques in order to get good rankings in search engines. Social bookmarking is what I would prefer from the above.
Would probably also depend on what your trying to sell. No point using social networking to sell tractors online.
im using all four. but rarely use oftware
I will Opt social networking in the choices but hope even sitemaps will also provide better rankings
None of these “techniques” have anything to do with search engine optimization.
SEO is the act of manipulating your website to make it easier for search engines to figure out what you’re talking about. You could argue that link building has a role here too as it will help boost your search engine rankings.
The closest thing you list to SEO is social bookmarking and social networking but neither have any noticeable effect on SEO. They do, however, drive real human visitors but that’s not going to help your search engine rankings.