Many photos one can get hold on have no dates or other information that gives an idea about when or where they were taken. Most of the less expensive ones are from 1939 to 1941, mostly taken in France and the Soviet Union, or during training before or during the first years of the war. On auction sites like eBay, they are often sold in lots of half a dozen to several hundred. Most are depicting Heer (Army), but a sizeable part are Luftwaffe subjects and some Reichsarbeitsdienst thrown in. The really attractive photos, with tanks, airplanes, Fallschirmjäger, Waffen-SS, etc, are sold separately and at much higher prices.
Identifying and dating photos can make your collection more interesting and sometimes even more valuable, at least in your own eyes. The photo above isn’t that expensive. It’s 9×14 cms, and thus slightly larger than most photos from the period. It might be worth a couple of Euros or US dollars at most if bought separately. What it makes it interesting, though, is that it describes a step in the story of the Heer. It is most likely taken during exercises back in Germany. The soldiers don’t wear the Y-straps (combat suspenders) which were introduced in April 1939, but not in common use until late in 1940, after the campaign in the West. This narrows down the period of the photo, but not enough, and it could still be from, say, 1938 or 1941.
Another pointer is the decals on the helmets. The national tricolor decal was discontinued in early 1940. Still, with plenty of M1935 double-decal helmets around, the photo could be of a later date, but together with the lack of Y-straps, it makes it more likely that the photo was taken before 1941. Now, some of the soldiers carry an interesting piece of equipment that gives yet another clue. Three guys in the center-left part of the photo carry the long magazine pouches for the MG 26(t), which was the German designation for the Czech ZB vz. 26 light machinegun. 31,200 ZB vz. 26 MGs were captured when Nazi Germany occupied the Czech regions Bohemia and Moravia in March 1939. Now, this narrows down the window of the photo, setting the earliest date at the spring of 1939.
A look at the trees in the background shows them to be without leaves. This makes me think that the photo was taken in either the fall of 1939, or the spring of 1940 at the latest. It’s my guess that the soldiers in the photo belong to one of the nine infantry divisions raised in the fall of 1939, and which were issued some captured Czech equipment. That would fit in with the estimate above, and make it more likely that the photo was taken in March or April, 1940. Most of those divisions saw action in France in May and June that year. So there we have it: I’m fairly certain that it was taken during those two months.
To make an analysis and identification like this demands knowledge of uniforms, medals and insignia, weaponry, history, and so on. Good reference literature and reliable Internet sites are needed, and being a member of discussion groups and forums with knowledge of the subject at hand can be a great resource, too. It’s a learning process, so don’t expect to get everything right from the start, or that it’s even possible to get that much information from a photo. As long as you derive enjoyment from it, you are doing it right!