A useful tool you can make yourself is a needlepoint thread directory. This notebook becomes a kind of “book of all knowledge” and reference for information about the threads you use.
For each thread you should have a page or half page. Include on it, the name of the thread, the fiber content, the type, of thread, then manufacturer, contact information for them, the place you bought it if it is an unusual thread, and the mesh size you like to use it on.
Then leave some space for notes. The needlepoint thread directory becomes a work in progress of threads and the way I use them.
I also usually stitch two 1 inch patches with any thread I try. One patch is Basketweave (on left). In addition to giving me a baseline for mesh size, this patch also tells me right away if the thread has variations in color because they will be so apparent.
Whenever possible use medium-to-light colors for these samples. Dark threads tend to obscure any stitching you do. This makes them hard to use as a reference.
Finally, I stitch one or more patches in decorative stitches, often ones which are new to me. This way I learn new stitches, but I also learn more about how the thread works. If I have ideas about how to use the thread, I also try them out here.
Another option is to use the stitch on a canvas and include a full-size picture of it in the notebook.
I use double-sided tape to paste these to the page and note the decorative stitch’s name and where I found it.
If I have a color card or if there is one on-line, I also note that. And I note similar threads, so substitutions are easier.
If you have a favorite shop, note if they carry it, and if you have your threads organized by type, note where it is.
With this needlepoint threads directory, it becomes so easy to plan the threads for a project.