This is a fantastic video from one of my favorite YouTube channels called "How to be a Great Game Master". It comes at things from a tabletop RP standpoint, but many of his points work very well with online Mineman RP. This is a great video from his "How to be a Great Role Player" series.
I have been working to try to improve my roleplaying/GMing and this channel, and this series specifically, has been very helpful. Give it a watch and let me know in the comments if you found it helpful.
This one is safe, but many of his other videos are for a game master audience. If you aren't a game master you might learn some things about roleplaying that you would rather not hear. Be warned.