I made some big screw ups cutting holes before I figured this out, and perfect ever since. (only works with plastic tote lids)
Trace the top of the net pot on top of the lid you'll be making a hole in. use 2 nickels or something to measure a standard distance from the inside of the circle, and make marks that same distance around the inside so you can draw another, slightly smaller, and uniform circle. When you trace this smaller circle, use an exacto knife; not heated or anything, just push barely hard enough that it breaks the surface of the lid; this is what you want.
after tracing the smaller circle, do the + sign like mentioned before, but when making it, push all the way through the lid. After you make it, the 4 tabs that now make up the inner circle will pop right off because once the plastic has that top cut, it breaks off easy.
Hope this helps