I am just wondering how people use conversations to improve, I know some people that just like a chat, I also know others that like to prepare a text to go through during the conversation, I like to push myself and speak about an unfamiliar topic that is arranged in advance 
What do you all do?
I usually chat about my life, my current and soon-to-be former job, my activities on LingQ, other LingQ members and my language skills.
I generally talk about what comes to mind at the time, or what my tutor is able to drag out of me. I have occasionally talked about lessons or other topics I prepared for in advance, and I feel that these conversations went much better. I do think I am approaching these conversations incorrectly, I don’t feel as if I am improving (although I am hard on myself, so perhaps I am improving and don’t realize it, although I doubt it). I always think that I should prepare for the conversations better, perhaps work on areas I feel I need to improve. I don’t think I am at the level where I can just talk about anything.
I think it depends on the level of fluency that one have in a language. As a beginner or low intermediate learner you should prepare a topic. A lesson or a podcast is fine. Or you talk about something you have done or you want to do (practise of future and past tense ) That is what I usually recommend.
As a high intermediate or advanced learner you should be able to chat. That is what I like when I have an English conversation. No topic, just what comes up to my mind, or the other participants mind.
I haven’t hold a LingQ conversation yet, but I do conversational classes in person and generally, I set a list of questions, sometimes related with a central topic, sometimes random; and although classes are very flexible and my student can talk about whatever he wants or whatever topic the conversation flow leads to; I may throw some of these questions in those situations he doesn’t know what else to say. questions that generally trigger interesting and unpredictible new topics. What did you have for lunch? how did you meet your girlfriend? which are the disadvantages of living in [insert city]? or stuff like, yesterdays this thing happened to me, did something like that happend to you before? or how would you react in a similiar situation? …
stuff like that, but of course, it depends on the level of the student, and, if he is focusing on some tense in particular. e.g. he’s problems using the past tense, we may talk about events on the past.