I like making up panels. When I was first shown what is involved, my boss opened up a panel on Upper Market in San Francisco and showed me a pristine panel saying "all electricians are proud of their panels". The one he showed me was very nice, he said "i used to do them this nice, but now I don't care I just do it nice enough".
There is no "nice enough" in making up panels. When you wire up a building, you may run miles and miles of wire, but no one will really see that when it is covered up (although it is still important to make those runs neat). The panel, however, will be seen over and over again by electricians for decades to come. It is important to make it look as good as you can.
Some electricians are concerned about slack in the wire, they loop wires and put "mickey mouse ears" on the feeders (circular loops). Honestly, if you plan your panel layout before you install the circuits, you shouldn't have to move them. It is way too much sacrifice for little return.
The way I do it, is I try to put as much length on the wire as I can but i confine wires to their own side, without much hope of switching them to the other side. I decide what is the right length to bend the wire to insert it into its lug, I measure it, and then cut a piece of sheathing to match that measurement, and I make all the wires the same length, i trie to make all the bends equal in radius, everything should look as uniform as possible.
If you can make an incredible panel, no one will care except the right people, and that is very important. I like the way I wired up those 3 panels recently, but I know each time I do one, it should look better than the last. It should look like a work of art.
