We often use the year then the momma's number; 1767 on # 67 etc. But then it gets interesting when we keep that heifer and she has a heifer. When we can't get calves tagged daily, like the last 2 years with my joint issues, then we do the year and start with 1 like coachg 1701...we get them all in, just start tagging and then watch who goes on who and then I record it. Takes me usually a day or 2 to get them all matched up. We use different color tags for the steers, either yellow or orange...and then green or white for the heifers. Makes sorting calves easy when we are getting them in to sell or whatever. When we decided who we are going to keep as replacements, then they usually get a second tag with the momma's number on it; and if it is mine it gets a white tag and my son's are green. We can change the color when they are in the chute.. Since we rent alot of pastures, we try to always make sure they have 2 tags when they go out, since you know sooner or later they are going to lose at least one tag.