Hi Jenn! Welcome!
My answer to you would be that I wish I was told to be diligent about proofreading my own work for spelling errors and grammatical errors such as verb tense congruence, singular/plural agreements, proper capitalization, proper punctuation, and proper usage of apostrophes. Also, be mindful of common homonyms like your/you're and their/there/they're. One's submitted work will be scrutinized by editors who will rate it accordingly.
I wish you all of the best of luck in your new endeavor!
Liam