Hey Anon! There are a few resources on the blog for this, I’ll link them here for easier access. These are some of my favourites.
Tracyjb’s Lackadaisy Expressions Tutorial: One of the best
The Grimace Project
Body Language Reference Sheet: Because we all know it’s not just our faces that convey emotion~
If anyone has any other resources to help anon out, just drop them in the ask and I’ll send them through.