I have wondered for a very long time if the trick of placing saran wrap over windows helps keep your home warmer. Well....I am happy to say that we have placed saran wrap over our windows and it has helped a ton! (We live in an older home with single pained windows and used to be able to feel a breeze come through the cracks. Now it just moves the saran wrap.)
I also have heard that it's not worth buying the saran wrap because its hard to tape it together and put over the windows...lots of people told me to just buy a kit. The kits are about $10-not bad and saran wrap is just under $2-lots better. One roll did all of our windows and wasn't to hard. Here is a trick to avoiding taping pieces together and save money in not having to buy a kit.
First, roll a long piece of saran wrap out (enough to cover the span of a window)
After you have a piece cut out take the roll of saran wrap and roll it over that piece while unrolling a new piece, you will want to overlap the last piece by about an inch
Continue this until you have a long enough piece to cover your window
The saran wrap should stick to each other...no tape needed except to tape the final piece to the window.
I did this about a month ago and it's still working:)