Personally, I use the following.
8, 9, 10, 12.5, 15, 17.5, 20, 25, 30, 35, 40, 42.5, 45, 47.5, 50, 52.5, 55
I consider the 8-10's critical, as there is a big jump in clicks between these, and 50-55 also, because it means i'm not guessing where 52.5 is... the other ranges in between the 5 yard intervals are there because it's easier for me to look up the clicks than work out what is halfway between 40 and 45 in my head.
I tend to use a newspaper to get a really firm focus on small type. It's easy to get vague ranges if you use an object that lacks detail.
I spend a lot of time making sure the 40+ ranges are repeatable, and then for double test i'll go and shoot a round at the club, as I can never remember the ranges of the targets there.