I would love to be able to give an extensive list of suggestions for a stay in Paris, but I really can't.
Once we dropped our bags in our petite apartment in the 3rd arrondissement, we went walking without plan. Strolling through narrow streets, discovering little shops and happening upon things like the Notre Dame.
So this is my suggestion to you. Pick an arrondissement and start exploring. Oh, and eat the bread. Eat all the bread.