Unfortunately I went through another hiatus in learning. It seems to be a character trait that I go through periods of being good and taking a rest when learning Mandarin as a hobby.
Here's a list of useful links to posts and articles (to be continually updated) in no particular order. Reading back in Chinese forums helps me get interested again. It just shows how much we can read and learn, yet still forget.
1) List of everyday topics to discuss. Practicing discussing about these topics with different teachers or language partners. One can practice the same topic with different people to gradually increase fluency and also increase vocabulary around that topic.
Note: many useful learning strategies in this thread.
4) Accent Improvement: more natural sounding tones - phenomenal post showing the amount of detail that one can analyse ones own tones for that holy grail of sounding native-like. Of relevance, refer to this Towards Better Tones in Natural Speech where one needs to stress the correct tone on key words when speaking to sound more natural whereas some other parts of a sentence, it's not so important. Some important practical advice here.
5) Honorifics in Chinese - this links to a Chinese honorifics wiki entry. I played with this a bit when communicating with newly met mature people on Hellotalk. Excellent resource and when you use it (and get it right), the feedback is pretty satisfying
6) Getting out of a listening rut - a very good thread that makes interesting observations on why a person may have much more difficulty listening despite a lot of effort. The most enlightening post is here on a 12th page.
7) Effective exercises for learning with a private tutor - not to be confused with 2) which has different strategies. Rote learning is an important way to success. A nice recommendation by @Tomsima for this book which I don't have, but learning some idioms for situational dialogues makes a whole world of difference.
8)Looking for more anki based material? It's here in the Subs2SRS Anki Deck Index
10) Worst advice when learning Mandarin - third point is great!
11) Drilling tones - takeaway advice is a lot of drilling on the same sentence is required. Chorus method requires drilling more than 20-30 times and this really opened up my insight. For some reason, I am quite happy to do the same amount of repetitive drilling in sports but felt in languages, it should be easier. Not so - you need to put your time in and no short cuts.
13) WorkAudioBook – a tool for listening practice (and subtitle creation) how to create .srt files and then troubleshooting the import into anki process
14) Independent Chinese study: review . The most popular post in Chinese-forums. How to learn Chinese away from formal classes. Simply awesome.
15) How to language exchange - this youtube video details the learning process of language exchange. It's the only video that I have seen that details the exact process within a language exchange session - further explanation with respect to input and techniques. Most other people talk about what you should do to find or keep a language partner rather than the content of how to learn within a session. Getting lots of commands can reinforce the acquisition process.
16) An interesting way and fun way to develop more interactions with people and helping your language skills.
18) The process of using a movie to help your Chinese listening
19) Mandarin YouTube videos to watch (link added on 1/1/2021)