RP TIPS FROM GOLDENEYESOFCAMELOT!
Read read read! Get to know the character you're roleplaying with. If the mun has taken the time to write up all this helpful information about their character, then do them a favor and read it. It'll benefit the both of you. You may save yourself some embarrassment and plot ideas may crop up while you're reading and then the two of you will be able to create something epic! It's also just common courtesy.
Communication is key! If you're not enjoying a thread or if you don't think that your writing style works well with somebody else, then don't just ignore them. Talk to them, work it out, and if you want to drop the thread, just be upfront and honest about it.
Have an open mind! Things aren't always going to go exactly as planned in threads. Sometimes it's like characters have minds of their owns and they want to take a plot in a direction you didn't exactly expect. In this regard, I would refer to #2. Communicate with your roleplay partner and prepared to not only roll with it, but make some adjustments on the fly.
Be proactive. Threading isn't a one-way street. Don't sit around and wait for your partner to move the thread along. Take what you've been given and make something with it! Contribute to the plot, make plot if you don't already have it! Both partners need to pull their own weight otherwise one half of the duo is likely going to get very frustrated.
Don't force ships. Romance is fun. Insta-love without any sense of development is not. Take some time to make sure your characters actually click and if they don't, it's not a big deal. Romance isn't the only plot point out there and just because the characters don't click romantically doesn't mean that they're a doomed for terrible plotting. In fact, sometimes characters not clicking is a fantastic way to create conflict.
Don't put yourself down! Now, anybody who knows me knows that I am guilty of this, but you need to remember that you're doing this for fun! Don't let other people spoil your fun and, most of all, don't spoil the fun for yourself. You are always going to be your own worst critic, but don't ever let that stop you because nine times out of ten, you are being way, way, way too hard on yourself. Roleplay is supposed to be fun, so have fun!