Travel to Paris in the months of March, April or October, November:   There are a few reasons for doing so.  During these months travelers miss the big crowds, hotel costs are less expensive, and flights to Paris are 20%-30% less than the peak times of May through September.

Buy the Museum Pass:  The Paris Museum Pass gives travelers VIP, no-wait-in-line admission to over 60 GOOD attractions in Paris.  Skip the hours-long lines at the Orsay and walk right in.   Don't wait at the Orangerie and enter on the special line for pass-holders.  Visit each attraction as many times as you wish while the card is valid.   This is a tremendous time-saver and secondarily, will save money.   For details see: http://en.parismuseumpass.com/

Take the Bus/Metro:  I love to walk while in Paris but there are times when transportation is needed.   Taxis are expensive and in some cases are slower than the bus or metro.   For daily transportation needs, but a Mobilis (one-day pass) for about 7 euros or look into the weekly Navigo Decouverte (valid Monday-Sunday at about 26 euros).

Visit the Louvre and Orsay in the Evening:  The crowds at these two attractions can be overwhelming to the point where it is not worth visiting.   At night, however, these crowds are significantly reduced.

Stay at a 2 or 3 Star Hotel:  Lodging is probably the most significant expense of a vacation in Paris.  I recommend staying in a comfortable, well-located hotel.   There are 2 and 3 star options that are full-service hotels that are very comfortable - if you know how to find them.   I post many of these hotels on the www.travelingprofessor.com website and in my book, "The Traveling Professor's Guide to Paris".