Prepositions: On my mind or in my mind?

Prepositions tell you the relationship the object has to the rest of the sentence.

The necklace is on the table, in the jewelry box, under the pillow, so on and so forth. Prepositions are short words that we take for granted (I interchange them more often than I care to admit), but it's important to get them right because they affect what the sentence is trying to say.

• Englishclub.com: English preposition rule - A simple site for English as second language learners.
• The Writing Centre, University of Ottawa: What is a Preposition?
• Betterenglish.com: Preposition quiz!