I happened to receive a pretty handy gadget from Spinzilla (which arrived broken, regrettably, but the good news is that the most important part was still usable...plus, there's always tape). Not only is this a nice tool to quickly identify the weight of any yarn, I have been using it to check my singles as I spin to make sure they are (reasonably) consistent. So, when I was spinning a sample for the yarn which ultimately was to be used for a sport weight cardigan, I made sure that my singles were a thin fingering weight (ideally, a little thinner than the line for fingering yarn on the gauge - and please pardon my chipped manicure below).
Sometimes, I take a photo of my wheel settings if I'm worried that I'll forget which ratio I was using so that I have it to refer back to later.
After I spun each sample, I let the singles rest, as I would if I were spinning a larger project. The next day, I plied them, then washed them in a no-rinse wool wash (Allure):
I'd love to hear any of your sample spinning tips in the comments!