The verbs to lie (sit, recline), to rise and to sit are sometimes confusing.

lie is something you do
lay is done to something
I lay my book on the table then lie on the couch for a nap.

rise is something you do
raise is done to something
I rise from the chair to raise the blinds.

sit is something you do
set is done to something
I set my keys on the table then sit to watch TV.

These rules do not apply in all situations, of course, but they cover most of the cases.