"The Trending 20" is a regular series where we round up interesting, informative and hilarious tweets from worldwide Twitter trending topics, fueled by young tweeters on the interwebs. Have one to submit? Give us a shout @huffpostteen.
Anyone who's made it through freshman year and lived to tell the tale will warn you that the first few months of high school can be a bit of a roller-coaster ride. You're suddenly thrust out of the comfort of middle school and into a world of football players, mean girls, chemistry exams and lunch-table hierarchies. But it's also when you'll make the friends who could stick with you for the rest of your life.
Last night, with back-to-school season in full swing around the country, upperclassmen took to Twitter with some words of advice -- and warnings -- for bright-eyed incoming freshmen. With the hashtag #DearGrade9, tweets ranging from serious ("watch who you call your friends. trust me.") to sartorial ("if your shoes still light up, get out of my hallways.") took over Twitter. Check out our top trending 20 in the slideshow below and share your own #DearGrade9 advice in the comments below.