My advice: don't stress. You've seen here that some Advanced GM's are more than willing to take somebody uncertain under their wing and give them some guidance, which is fantastic- though, I have to say, there's something to be said for just throwing yourself in and practising and there's really no substitute for the latter.
While there are some tips and tricks, which others have given you, to make your writing look and feel probably more interesting, my personal #1 rule is to avoid using the same word in a paragraph if I can help it. It's something an English teacher told me when I was seven, and I'm still using it. I don't know exactly what it is, but it does seem to make text more interesting.
That said, there's no rule without exception. My 'don't repeat' rule is instantly binned if there is value to be gained from repeating. Think about the tone you want your writing to carry and work toward it. If you want your work to be, for example, 'exciting', you can literally google that shit - you'll get advice to the effect of short sentences to simulate speed - but, then, you might find that a long sentence once in a while will simulate breathlessness.
- Said is dead. While the phrase 'X said/said x' is a easy go-to phrase it doesn't really carry emphasis. So I would advise to study on other emotional expressions to write or their synonyms. Repetitious use of said - as easy as it can be - is pretty boring.
"I don't like to contradict, but
I beg to differ. For me," Said Jig, who was outlining an example while far too drunk to do it properly, "a 'non-said'-word should only be used to emphasise one instance of direct speech every once in a while. Otherwise, I simply use 'said' if I feel that the speech needs a 'said'-word for flow but there's nothing really to express, or simply, you know," Jig's fingers drummed on the table, "Say literally anything else instead just to break up the speech."
- Learn the tropes and the cliches. Whether to avoid one or pull-off a well exercised inclusion of the other. So if you dare TvTropes will probably be the graveyard of your past-time.
I really do recommend TV Tropes. I've spent a few years wiki-walking TV-Tropes, and now I see tropes everywhere. It doesn't push things into pigeon-holes but, rather, gives you a broad outline to work from and see how everything fits in. The interest, as far as the reader is concerned, comes from your own individual variation and flair which is something you'll develop over time.
Apart from anything else, I'd say that many GM's in Advanced would rather take a 'weaker' player over a 'stronger' player if that 'weaker' play shows more interest, commitment, and a more cooperative attitude. Writing like Keates does not an Advanced Player alone make .