1. When you have any tweaks/settings that you normally apply (so that you don't have to apply them again) and any security updates/SP1, 2, 3 versions, etc.
2. Then another when you have installed your AV, firewall and other common applications/tools.
The reason for a second is that if you change AV/Firewall etc. do you want that on an image restore. I however failed that test as I would probably have done it after 2. above as my common application choice has remained the same for a number of years, avast and outpost pro firewall.
You don't want everything there as you are considering that as your bare bones to avoid having to start from scratch again. After that I do a weekly full image of my partitions you could with true image go for a monthly full image and incremental image weekly.
I still use an old version of Drive Image 7.1 which doesn't support incremental imaging hence the weekly full image backup, but I keep 5 copies so that I have a months worth of backup and not just the one file.