For a movie featuring ghosts who love Calypso music and cocktail shrimp on the rampage, Beetlejuice is pretty classic when it comes to basic plot structure.
The story roughly follows a basic three-act narrative that most movies do. First one thing happens, then that leads to another, then another, then another, with increasingly nutty consequences along the way.
Act One is all about establishing the world of the Maitlands. They're just a quaint New England couple who want some peace and quiet. Then they die and are forced to live with the Deetzes, who want to destroy everything the Maitlands loved in life. We hate it when that happens.
Act Two leaves the Maitlands with their only option—scare these people away. Trouble is they're not great at it, so they're gotta reach out for some help in the form of Betelgeuse. This doesn't go exactly as planned. Nothing really does when you're dead.
In Act Three, Adam and Barbara face the Deetzes and Betelgeuse for the final time and manage to win back their house (and get that peace and quiet they've been wanting all along). It's as happy an ending as you could want when you're already dead.