With modern footwear, the only thing you should have to worry about are blisters. If you get a good pair of boots, there shouldn't be a break in period for the shoes, just your feet. As for the blisters, I have tried wearing pantyhose style stockings under my regular socks, but I didn't like them as they were too tight and allowed my feet to slip inside my boots.
Now, when I get new boots, I carry a few different sized bandages (Band-Aids) with me for the first couple trips. As soon as I notice an area rubbing on my foot, I apply a bandage. I also apply the bandages the next time I use them, but everything is usually OK, by the third day. (I have also tried using moleskin for this but I like the regular bandages better.) Also, I find I need to apply the bandages longer for hiking boots with full leather uppers, but the time needed will be determined by how stiff the leather is.
As described above, I have also tried soaking my leather boots, letting them dry for a bit, and then wearing the damp boots for several hours. This does allow the leather to conform to the legs more quickly, but I still usually need to use the bandages to get past those first couple uses.
That said, I still prefer to start wearing my boots the traditional way, without soaking. If I have the time, I'll apply saddle soap, mink oil (is my preference), or any other leather conditioner very liberally and let them sit for a couple days to a week with a towel or application rag covering them. (Dust will collect on the boots and dry the leather conditioner if they are not covered). I'll wipe them clean and then do it again. I'll do this 2-4 times, until the leather is buttery soft. This will also make them completely waterproof.