"serging the edges" - if you have a serger - a type of machine that trims the edge and sews over it in one step
"overcasting the edges" - if you have a zig=zag machine - just do a narrow, long zig=zag stitch along the very edge - minimizes fraying during washing and drying
even doing a straight machine stitch about 1/8 inch from the edge helps minimize fraying