my mother showed me how to fold plastic bags that take up very little space.
lay the bag down and fold in the sides the way they were folded. then fold in half sideways. fold in half again sideways. you should have a long strip. then start at the bottom and fold bottom left corner over to right side. this should form a triangle. then just keep folding right side to left, left to right etc. until you get to the top. the loop of the handles should rap around your little triangle. this lays very flat and doesn't take up much room in your purse or pocket. should be about 4" x 2". hope this helps.