I use blank magnetic PVC labels with an indelible marker pen plus someone with neater writing than me!
Handy when you use pellets from different manufacturers especially those with names like Perfect Mix, Longhorn Blend or Signature Blend. Colour coded ones can also acts as a reminder as to whether the pellets in question are best for red meat, white meat, fish etc allowing for further info.
I'm new to Treagering but I have had other grills and what I found handy was to leave the bag or container of pellets on or near the grill. When I changed pellets I changed the bag or container. hope this helps.