I know some people have a great enthusiasm for book-keeping in wargaming, but I personally tend to avoid most of it. However, when running an imagination campaign with a manageable number of regiments, each with their own name, a little bit can be rewarding. I have been keeping a simple spreadsheet of my units for this campaign, and writing down if they were present in each battle or skirmish - plus adding any notable feats of arms that stick in my mind. The process is pretty straightforward and undemanding, plus it gives some decent regimental 'narratives' over time. Here's a few typical examples:
Luftberg Infanterie Regiment of Negrelli (No. 4)
Present in Passditz battle-line but unengaged. Did not take part in rearguard.
Fought in Redoubt-storming near Spitzburg, flanked enemy and nearly won fight, but was forced to retire.
Fought at Froschbach. Attempted to attack flank of Grenadiers over marshy stream, but took heavy losses in stream.
Aschenbach Kurassier Cavallerie Regiment Von Kurbitz (No. 2)
Fought in Passditz and routed opposing cavalry.
Took part in pursuit after battle, routing Dragoon reg. D1 and captured General Van Der Dijk, but was caught by the fire of 3 enemy infantry regiments and greatly weakened by heavy losses.
Recovered and refitted in reserve, then was in action again at Froschbach. Charged repeatedly and was heavily engaged.
As you will see from the two examples above, the histories can quickly begin to take shape. I'm hoping the process could eventually begin to make more and more 'real' connections, such as two opposing regiments that repeatedly tangle with other could develop a rivalry, or perhaps a unit that fires particularly effectively in a few fights may be judged to have a particularly zealous drillmaster and get a permanent bonus, etc. The possibilities that emerge over time are good for firing the imagination!