1. Why they joined: Were they second sons of noblemen? Upper middle classes looking for status? Following family tradition? What other motivations might someone have to choose a military career?
2. How they advanced through the ranks: I know that commissions were purchased until the Cardwell reforms in the 1870s, but did promotion occur any other way? Did a majority or a minority of officers go to Sandhurst? Just how wealthy did someone have to be to purchase, for example, a colonelcy? How did promotion happen after the sale of commissions was abolished?
3. About daily life: Beyond actual wars and battles, what was life like? How often did they train/drill? What did they do for fun? How did they socialize amongst themselves and with civilians? Were they expected to maintain a certain lifestyle? What kinds of behaviour might get them into trouble/cause a scandal? What kinds of things did corrupt officers get away with?
4. About retirement: Was it more common to retire or to serve for life? How did someone go about retiring and what did they do afterwards?
I'm especially interested in the British Indian Army, but information about the plain old British Army is fantastic as well. I'm also trying really hard to grasp the Victorian class system and where army officers fit into it, so information along those lines is very useful too.