Remember, love. It's the quality of the post, not the quantity of the words.
Ah, descriptions. Always so fickle, always so tricky. I still have a hard time finding the words to describe a feeling or scenario. I suppose some tricks I use is to find pictures that resemble a setting or person or something in the RP, then try to find the words to describe what I or what I think my character feel about it. Smells, tastes, emotions. Incorporate some of it in your writing. Use similes and metaphors and fluctuating sentence lengths. Just feel the words.
Additionally, write when you can and write freely. Read when you can, and look up writing tips online. Find fancy words, don't be afraid to break a few rules, and always remember to have fun.
If you wanna chat or use me as a practice dummy, don't be afraid to hit me up. I may not be the best writer, but I love to help a new friend out! ;D