I don't have a 'notebook' that I use all the time.

But I have an agenda and I take notes there. I either write my lecture notes in another notebook, in the notes section at the end of my agenda or I open a word file on my tablet.

However, if I don't have anything with me, I definitely take notes on receipts.

I take one of the previous receipts out of my wallet and immediately write down what I am going to write down.

I take notes on sticky notes.

Or the ones without adhesive...

And most importantly, I take notes in my one-person whatsapp group titled 'NOTEBOOK'.

Excellent tactic.