In that notebook I also write down ideas for domain names and the second I get home I try to buy them.
I never search for a domain except through my provider with the intention of buying it right there, right then because there are people out there who can see domains being searched and will buy them out from under you if you don't but them as you search.
I learned the hard way on that one as I once searched and didn't buy on the spot, came back and found that the domain had been snapped up by some guy in Hong Kong who has a reputation for doing just that.
I use business cards. Cost me about twenty bucks for 500 and they have made me thousands.