Just divide a right angle into 3 to get you a decent 30 degree visual and buy a box of files sized for the chain you use.
You will appreciate a few minutes to rest and allow the saw to cool before topping off the fuel and bar oil while you file.
The best tip is to look at a chain that is fresh from the box and replicate what you see.
Keep the damn thing out of the dirt it's not a skinny rototiller!