I'd recommend using keyword research, competitor analysis, and other professional staff, of course. But all these methods require some experience, time, and budget. However, there are quite a few things you can do to whip your SEO into shape.
1. Do at least some kind of keyword research
Keywords are one of the pillars of SEO, so it'd be a shame to ignore them completely. As I've said, there is nothing better than professional services, but the monthly subscription can fly into a pretty penny. Still, some free services give you at least a general idea of the required keywords.
Note that the bigger the site is, the more general terms it uses to rank for. You can use this trick for your blog as well. If you're just venturing off into your blogging journey, the surefire formula is the following: begin with a big set of long-tail keywords. They have less traffic, but your chances of higher ranking are bigger. Once you've fetched some SEO authority, start optimizing for more general keywords.
2. Great content plus SEO equals unbeatable combo
Content is still the KING. A well-optimized blog post that shares value and relevance has higher chances of killer rankings compared with the post that is well-optimized only. Therefore, you should never choose between SEO and quality, choose both of them if you want fast and long-term results.
For that, I'd recommend doing some competitor research for inspiration and trendy topics. Or you can go the other way, and feature a lesser-known topic using your own hands-on experience. Another thing that scores some extra points is a post structure. There should always be an intro, body, and conclusion. Among other things to consider are:
- a post title (choose engaging/contradictory, etc. titles) - a character limit between 55-60 so that it is shown without breaks in the SERPS+target keyword
- use headings to define your structure (wisely!)
- write in short paragraphs (2-3 sentences)
- add relevant links to trustworthy sites
- optimize the length (longer posts perform better)
3. Optimize your meta title and meta description
Meta title and meta description are some of the most important meta tags in SEO-optimization, which affects the formation of an attractive description of the web page in the search engine snippet. The content of the meta-description is not considered as a ranking factor, but it may affect the page position in search results indirectly by forming an attractive snippet description (annotation) which helps to increase clickability.
4. Optimize your images and other media elements
Media optimization allows you to reduce load time and increase the site speed. Although it won't boost your speed that much, it'll still make the difference between your site either gaining or losing readers. So you should deliver your images in high quality and the right format, dimension, size, and resolution while keeping the smallest possible size.
I think these are the basics of SEO-friendliness. The list is not excessive, of course. If you have any other questions, I'll be glad to answer them.