Vanessa,
If you turn these sentences into statements rather than questions, I think you'll see the subject. Who is doing the action? Also, whenever you see a phrase starting with a preposition such as "on" or "for", the noun will usually be the object of the sentence, not the subject.
1. Your sister babys sits for the Martins.
► The subject is sister. The verb is sits. Baby is an adverb describing sits. For the Martins is an object phrase. Martins is the object of the sentence.
2. I may spend the money on a new tennis racket.
► I is the subject. Spend is the verb. On a new tennis racket is the object phrase. Racket is the object of the sentence. Tennis is an adjective describing racket.
3. Betsy Ross's house can be found down the street.
► House is the subject. Betsy Ross's is an adjective describing the house. Can be found is the verb. Down the street is an object phrase starting with the preposition down.
4. Abraham Lincoln's first home stood here.
► Home is the subject. Abraham Lincoln's and first are both adjectives describing the home. Stood is the verb. Here is the adverb describing stood; where the home stood. It stood here.
5. The girl rushed down the stairs with her school books.
► Who is doing the action? The girl is. What did she do? She rushed. Where did she rush? Down the stairs. With her school books is an object phrase starting with the preposition "with".
6. You did not bring a note for your absence.
► Who is doing the action. You is doing the action. What is the action? Bring a note. The object phrase is for your absence. The object of the sentence is absence.
7. Our vacation does include the day of Washington's Birthday.
► Vacation is the subject. Does include in the verb. Of Washington's Birthday is the object phrase starting with the preposition "of" and ending with birthday, which is the object of the sentence.
8. The mouthwatering smell of fresh bread came from the bakery.
► Smell is the subject. Mouthwatering is an adjective describing smell. This sentence has two prepositional phrases, of fresh bread came and from the bakery. Remember the subject of the sentence comes before the preposition.
9. I have seldom seen such a colorful sunset!
► I is the subject. Have seen is the verb. I saw who or what? I saw a sunset. Therefore sunset in the object of the sentence.
10. [You] Always put a collar with identification tags on your dog. You is the implied subject. Put is the verb. There are two prepositional phrases here: With identification tags and on your dog. Remember that the subject always comes before the prepositions.