Wow this is the million dollar question that many English learners would like the answer to! My advice would be to first try and get a sound knowledge of English grammar, particularly verb tenses, articles and preposition. Boring but these are the key building blocks to advancing your English in all areas. Next you should develop your vocabulary skills, by reading as much as possible and noting down any new words that you come across and try to memorize these words. Finally try to learn from your mistakes and don't repeat them. Don't worry about making mistakes, this is natural whilst learning any language, try and turn a negative into a positive! Basically it's not an overnight process but takes time, dedication and perseverance. Good luck!

Two things that I would like to say. 1) don't worry about making mistakes! It's how you learn. Use this site to your advantage and have people help you and correct your mistakes so that you can learn 2) you will always make mistakes. It doesn't matter how perfectly you speak/write or how long you have been doing it, you will still make errors. I am a native speaker and I still make a lot of mistakes. I am a terrible speller, and grammar occasionally slips me. No worries bro I hope this helps :)

First of all, I think a lot of the grammar that ESL students are required to read and understand is incredibly intense, and I wouldn't expect anyone who does not speak English as their first language to know how to construct sentences in these ways. In Australian schools, we actually don't learn grammar - it's a really small part of the curriculum. I can remember studying English Literature in year 11 and being given a grammar book to study - for the very first time in my life! Having said this, yes, grammar is a very important part of learning English, but there's no point in learning how to construct sentences exploding with top-range grammar, if you can't actually use it correctly in a real-life sentence. I think that if you want to improve on your English skills, the best way to do so would be to practice conversationally with others. Rather than trying to memorize grammar rules and conventions, try using them in normal conversation and start to feel confident that you can use sentences correctly. If you make a mistake and somebody corrects it for you, practice writing other sentences using the same structure a few times, so that your brain has practiced the sentences and corrected the structure. This will make it so much easier to understand English, and you'll be able to read and write with more confidence.

I agree with Teacher_Greguk. Although a piece of writing free of errors is ideal, it is probably more important to accept the fact that we learners are bond to make tons of mistakes and to see mistakes as something beneficial to us. People who make no mistakes are those who try nothing at all. People who try gain experience. The experience help us do better next time. Have fun!