I leave a roll of trash bags in the bottom of the trash bin, so it's where I need it when I need it - instead of taking up place elsewhere or getting lost.
I do this for all trash bins. In the kitchen, at the toilets, at work, in the garage etc.
Also, with all the different sorting these days, I've decided not to sort the plastic, paper, glass etc. at the source, but just use one big container for all the clean stuff. When it's full, I'll take it out and sort it at the actual trashcan outside which is the place where it actually needs sorting. There's no need to keep 5 or more different trash containers under the kitchen sink to be emptied separately.