This is from diynet.com, a transcript of what Lily says during the swatch segment.
Correct Measuring of Swatch
Instead of measuring your swatch and your knitting flat on a table, why not get a more accurate picture of "the real world"? That is, you'd wear your sweaters in a vertical position, so why not measure the swatch and sweater upright as well?
This is known as a hung gauge, a method by which you let gravity take its toll. Use pushpins to place the swatch up to a corkboard, or use straight pins to fasten the swatch to a hanging towel on the towel rack. I've even taped the swatch up to a wall using masking tape or duct tape. Again, this emulates "real life," and the gauge may change in this position. This is the position use to match the dimensions of the pattern.
Weight With Clothespins
Sometimes it's not enough to let a swatch hang. If it's inelastic yarn such as cotton or silk or rayon, or if the gauge is on the loose side and the fabric is not firm, or if the yarn is very heavy and bulky, use clothespins along the bottom of the swatch to give a more accurate measurement (figure B).
Again, I don't know how much of this is true or not, as I've never actually finished a top.
I'm cool with whatever works, hehe.