One of my favorite tricks she has is her technique for knitting the gauge.
She suggests buying only one skein of the yarn you are considering for a project, now I don’t have that much self control. But it sounds like a great idea.
Use the needle size recommended, or the size you think will give you gauge (I am a very loose knitter and usually go down two sizes). Cast on the number of stitches that the yarn label recommends for 4 inches square, plus add a few stitches. Knit garter for 3 to 4 rows, now knit the stitch that will comprise the majority of your pattern, (lets say that is stockinette stitch). Knit in the pattern stitch for an inch or two, now switch to stockinette stitch, (if you are not already using that stitch) and in the middle of the swatch knit the corresponding number of purl bumps as your needle size you are using. Measure and see what your gauge is.
OK, now I know this isn’t washed yet, but switch to the next likely needle size (stitches look too loose? go down a size. Too tight, up a size) now knit several rows in SS stitch and then knit the corresponding number of purl bumps in the middle of the row as the needle you are using. Continue in this manner until you have a swatch with all of the possible needle sizes that you think are necessary.
Continue in this way, when done, wash as you would treat your garment, and let dry, now we measure.
I have also discovered swatches that have the “before" 4 inch square” outlined in a running stitch of contrasting thread, then after washing it is very easy to see how the measurements change.
The beauty of this method is that we have one swatch, with several different needle sizes to refer to. And if you actually had enough self control to buy only one skein of yarn, at this point you might think “NO, not that pattern, but it would look good for this ____”. Your swatch is done, and it is easy to refer to the size needles that were used.