Making pattern swatches is what I love doing when I am in-between projects. It gives me peace of mind to see the yarn I want for a project works good with a certain pattern.
After I make the swatch I always add a tag of the following things:
* Brand of yarn
* Weight of yarn
* Hook size
* Gauge (I sometimes leave this out if I want to try it with different yarn and relevant hook)
* Name of pattern / pattern repeats
Tagging swatches is extremely helpful when determining whether a pattern is suitable / good for a crochet garment for example. If I am not satisfied how a swatch looks like with a particular pattern, I try bigger (or smaller) weight of yarn. For me, the most important information on the tag is the pattern repeats, and that info has saved my nerves from wrecking on multiple occasions.
Do you make swatches? What method do you use to note down / record swatches' essential information?