Then Gamemastering is for you! Brian Jamison, a long time roleplayer and GM, has written this book with all sorts of information for other GMs out there. The book is systemless, so there’s tips in there for you no matter what RPG you play.
I usually get stuck as the GM in the RPGs I play, so I’ve already started digging into this.
Keep in mind that while the book is free, you can always support the author by buying an actual print version of the book, Gamemastering, on Amazon for $30.