For the members who know little about SEO, where would you advice a webmaster should start?
If someone have basic knowledge of SEO then there are many ways to learn more. If you want to practice for free .... create Web 2.0 properties for free at blogger or wordpress or if you want to earn more reputation then book a domain and hosting and start SEO link building for that website.
As, SEO company or freelancer, if you can proof that you have knowledge then you can get more projects and own website or properties or any other ways (Like Forums, Communities like quora, reddit etc.) where you can proof yourself is best ways to get attentions of people.
What do you think is the best way to build backlinks?
First of all check niche market, website reputation and spam score, if any websites pass these three steps mean you can get backlinks from there.
Second website should be real. For example PBN, many webmasters bid on auction and buy expired domains with good DA, PA and set a blog website or something related according to name (By check googlel cache also, if exist) ..... after that they start marketing that get high quality backlinks for "Home Improvement" from good DA websites, but these types of links are not more effective than back links from real website. Manual blog outreach is best example to get high quality backlinks.
Third important thing is contents based back links. If you are able to get back links from mid of contents its more beneficial then other links.
Fourth point is dont consider for do follow backlinks only because search engines knows very well about your online activities, if you are getting only do follow backlinks means you are trying to boost site ranking by paid or something suspected activities. If you are getting do follow and no follow both types of backlinks then it can be considered as natural link building.
There can be many more creterias .... all points are not coming in mind at same time