[omarhaneef]

This is the closest to what I do myself -- I always have pen and paper on my desk -- but the real issue is that I don't take a note when interrupted because of social pressures (its rude to ignore someone for a few seconds). I don't even do it for myself for self interruptions because I forget to.

[kelnos]

That problem is solved through humility and social graces.

"Hold on a sec, I just wanna write down what I was doing so I don't lose my place."

If you want to add more, after writing it down, you can follow up with, "sorry to keep you waiting, but when I get interrupted I often forget some useful details about what I was working on, and I want to get that down before it leaves my head".

(The "when I get interrupted" is a bit of a cheeky way to point out "you are imposing on me, so the least you can do is allow me this".)

[cbm-vic-20]

It's rude to interrupt someone without giving them the time to put down whatever it is they're doing. Even if it takes more than a few seconds.

[idealstingray]

For me, a quick "hang on" or "sorry, one sec" acknowledges people enough that they don't feel ignored while I make my notes, and is also scripted enough that it doesn't usually knock the thoughts out of my head.