@Irena

I agree with you that the other skills are equally important in order to develop your speaking skills. I normally start learning languages by writing and reading and the speaking follows naturally. I just wanted to give some ideas for those, who don't have any other chance to speak and want to practise.

@Guyomar

Yes, a comprehensive input is very important and when you had a lot of input it's easier to start speaking. I had my first ever Spanish conversation after three months of mainly reading and writing and it already lasted half an hour without any problems. I've seen several learners complain when being told "watch videos, listen to podcasts". They insisted that they needed "a real person" to guide them, otherwise they wouldn't be able to learn. And that is totally a myth.

@Alice

I agree that talking to yourself isn't the same as talking to a real person. But language classes are a luxury. Many people don't live close to a local language school and one-on-one online classes are for the majority of people around the world either not affordable (an hour of English class costs more than the monthly income in Venezuela) or they can't transfer money internationally (e.g. learners from Iran). Often when learners post ads for finding language exchange partners, teacher or tutors respond and offer their paid services or users from wealthy countries suggest "forget free language exchange, book classes with a professional teacher". But it's easier said than done. And apart from the financial aspect are independent language learners capable of becoming conversational in a language without a teacher or language partner. It's more a matter of motivation and using the suitable methods and resources.

Beyond shadowing and finding ways to produce the language alone, I think the majority of the time should be used to listen to and read appropriate material for one's level in the target language. This applies whether one can afford teachers or find partners or not. Therefore it may seem that people who can't afford lessons or find a partner are at a huge disadvantage, but in fact, they don't have to be, if they let go of the popular idea that speaking is the most important part of learning a language.

For some languages, it's easier to find appropriate material than others, but in English, the language for which there is usually the most demand for partners, there is so much free and interesting material, and many ESLteachers have taken the time to group videos, articles, and podcasts according to the student's level. I advise people to find these recommendations.

I started speaking Spanish and Russian again after a period (almost a year in the first case, and six weeks in the second) of silence in which I wanted to focus exclusively on input. After 1-2 conversations, I was able to speak as comfortably as I had previously, and also use many new words and constructions that I've only come across in reading or listening, but never "practiced" or used myself in any speech or writing. 

The biggest obstacle to acquiring English (or other languages) isn't the lack of partners, the affordability of lessons, or the absence of opportunities to speak. Sure, it can be motivating to talk, gauge your progress, get feedback from a native speaker, and lessons can give structure by keeping you accountable. However, I don't think all this is essential. The biggest obstacle is the idea that speaking is the most important part of the process, and that you won't get anywhere significant without it. This leads people to give up, instead of spending time on the most important part of the process, which is free.

Make yourself a teacher of the target language to others.

My Chinese pronunciation wasn't good enough during my study in China for 3 years. I didn't pay attention to the tone before, my focus went mainly to reading and writing at the time.

After I went back to my country and started teaching as a private tutor, I forced myself to brush up the tones every single day, I literally memorized each tone of single words. My brains worked twice harder due to the responsibility of being a tutor unconsciously.

It does pay off eventually. 

Thank you for your detailed information on self-teaching methods.