Always a system. lol
I use the bands on the left leg to identify which pen the chicks came out of - that will tell me who the father was. When known, I will use the right foot bands to tell me which hen. That isn't always known, as each pen as 2-3 hens in it. sometimes, the eggs are easily distinguishable, or I've separated the hens to be able to tell which hens laid what eggs.
Starting this year, I also toe punch, but the bands are easy to see in a group. I start with these little rubber bands, in three different sizes, until the chicks are about 3-4 weeks old. Then I will go to colored zip ties until they are old enough to put numbered leg bands on.