put lots of keywords, search on sites like alexa for keywords. and put all popular keywords related to your blog. description also try to find most popular one. robot tag i do not know Ivan. Is it robot.txt ?
Just add robots as the value of the name attribute and index, follow as the value for the content. All should be within the opening and closing of the meta tag. you can see my blog post on that. copy and paste the the script to your blog and save it.
SERP is more about the combination of page rank and web content. Google releases SERP once every three months. The uniqueness and quality of your content and the number of backlinks pointing to your site is what determines your page rank. That's why you need robots enable to allow search engines to crawl through your contents whenever the approach/come around your site