You'll have to bare with my lack of knowledge but I always get confused by warfare from about 1820, onwards. I know that prior to that, you'd have your cannons, lines of infantry, cavalry on the wings etc. However nearer to the 20th century I find it gets blurred. There are iron clad ships, gattling guns etc. So, my question is this, what would a Franco-Prussian battle look like? Would you still have lines of men firing at one another, occasional cannon fire etc? I have read that there were trenches in the American civil war which wasn't too long ago, would men have been in trenches? If they were fighting near a town would they use buildings to shoot from etc? Was cavalry still used? Or say rank fire by men? Sorry if I have worded this question badly, thank you to anyone who can answer.
Unfortunately I don't have that much time to write a thorough response (it's almost bed time), but I'll give you a basic idea of what it would have looked like.
Essentially, picture something more like Napoleonic warfare than WWI. It really is between the two (both in terms of technology and place in time) but the tactics of individual battles was much more reminiscent of the early 1800s than the First World War.
Battles were still fought with infantry and cavalry, generally following the tactic of artillery bombardment. Strategies like the Creeping Barrage had not yet been created (in which artillery fires a short distance ahead of advancing infantry), but artillery -- at least, the German artillery -- was capable of firing quite accurately from around 3 kilometres. Additionally, German artillery was breech-loading as opposed to the muzzle-loading of the French, the former of which is far more efficient to reload & a simpler process.
Trenches weren't used all that much. Even in WWI, although anyone with half a brain should have realized otherwise, ancient military tactics (send your soldiers charging into the other side's soldiers while they do the same thing) were still prevalent -- despite the fact that machine guns would mow down hundreds of troops before they could even approach.
As for machine guns in the war, gatling guns & the like were used but were not particularly prevalent as far as I know. They were still quite experimental, expensive and something that required training to use. I know that the French had their own experimental 'machine gun' (which was quite primitive and in the VERY early stages of adoption by the army), but it played a relatively small role.
Sorry I don't have time to write more. I hope this answered a few questions.
Are you asking about the Franco-Prussian War in particular, or rather just general military tactics of the time? If the former, there aren't many examples to choose from, just because of how fast the F-P War was over.