Getting really "into" a period

How do chaps these days get into a new period- with all that gamsey trash about how do they know (assuming they care) that they are getting it as right as they can.
 When in days of yore I was more of a collector and modeller than a pure wargamer- still am up to a point-  one read the books . There was even, I recall , a discussion in the pages of Mil mod about "fidelity to source"  meaning  getting it right according to the sources available for a given uniform or type of warrior. Given that there were and still are  differing  sources  for some uniforms at different times this is perfectly undestandable.
 For me its much the same trying to sort out a"new" period- not that there is any such thing really as I've had a go at most periods in my time and even those I don't currently have armies for I've probably got a book or two. I might saell armies whenI get fed up with them but never the books.(I only ever sold the books for a given period one- ACW- regretted it ever since- even bought some of them again) .
 As readers of previous posts may be aware I've recently dusted off those few Late Medieval units still in my collection with a view to re-activating those armies. I last had armies for the Hundred years war in the mid Nineties the old Hotspur range  but sold those one around 1997. Nevertheless  I still have the books- A dog eared Penguin copy of Froissart . Jim Bradburys study of the Medieval Archer Ian Heaths "Armies of the Middle Ages"  Oman of course and Colonel Burne  a couple of Ospreys but to be honest much of the stuff is a bit out of date- especially Oman and Burne- scholarship has moved on . So I needed to update. Over the intervening years I'd bought a few volumes-most notably Strickland and Hardy "The Great Warbow"- an absolute cracker this- but despite that I still felt a bity short on up to date info. So I added a few volumes- Juliet Barkers study of the Agincourt campaign Matthew Bennets Osprey on Agincourt and a couple of others.

The "Medievals" I already have. the Knights are  the Earl of Oxford and his retinue as at Poitiers. There was an Earl of Oxford at Agincourt- but not this one.

 At this point I haven't yet painted another figure- well  only half a dozen or so -  but one of the things I "re-realised"  is that "Medievals" is not one period but many - like "Ancients" only more complex so a simple example- The Battle of Poitiers was fought in 1356 , Agincourt in 1415- 59 years apart. So up to a point  having troops for Poitiers and using them for Agincourt would be like using Marboroughs army for the Seven Years War or Napoleonics for the ACW. Not quite so bad as things didn't change so fast and the archers are very similar indeed but I'm sure you get my point.  If you are going to get into a period surely you want to know who did what to whom  How and what with  Oh and what sort of trousers -if any was he waering when he did it ?. If you don't want to know that then what are you fiddling about at?
Idiot books- nee "Army Lists" however do this kind of stuff all the time and I've  seen all sorts of travesties on "Medieval" wargames- though not recently - the period seems to have gone out of fashion as Henry Hyde recently remarked- but 13th century  stuff rubbing shoulders with 15th century was nor unusual back in the day- even did it myself. Now I know better.
 My point here is simple- Army lists and Ospreys do not an Historical Wargamer make.