Cast on 20 stitches using the long-tail cast-on. Remember that you are knitting the first row when using this cast-on, and knit 40 rows.
I did my first swatch using a size 8 needle. I ended up having to go up to a 9 to achieve the correct number of stitches.
When I did my gauge swatch, I also knitted one side of the swatch using a garter stitch selvedge. I like how this selvedge looks, and it also makes it so much easier to pickup stitches. This is totally optional and a matter of personal preference.
I do not recommend doing this selvedge if you think that you will forget to do it on a row. If you happen to knit straight across and do not do the selvedge, it will stick out like a sore thumb; and you will have to "FROG" back to fix it. To do the garter stitch selvedge, do the following:
Slip the first stitch purlwise with the yarn in front. Move yarn to the back and knit across the row.
Begin every other row with this technique for a nice, finished edge. On the other side, you will just knit the first stitch. This will give you a comparison of the two edges, and you will be able to choose which one you like best.
After knitting the 40 rows and checking my gauge, I used the swatch to practice the "reversible phoney seams." I did one 3 stitches from each edge.
AGAIN, if you choose to do the garter stitch selvedge, BE SURE you do it every row. Your edge will not look good if you forget and do a knit stitch at the beginning of the row. The only way to fix this is to rip back. -- Just something to consider...!