Like "lie" and "lay," sometimes it can be difficult to figure out how to use "sit" and "set" correctly. The word "sit" means to assume or be in an upright position, and it is almost always an intransitive verb, so it doesn't take an object. Example: I never sit in the front row at a movie theater.
The word "set" means to put or place something, and it often takes an object. Example: They set the plates on the table.
Here's how to conjugate both verbs:
When writing, if you mean to put something down, use "set." For everything else, use "sit," and you too will be sitting pretty.