The problem is there is plenty of good practice but every profession has 
its power structures and people tend to appoint people like themselves. 
I trained as both an archeologist and historian but this is often not 
easy given the structure of courses. Both disciplines need time and 
experience to become competent - though most of the rest of the list 
don't have to work on medieval latin documents. To take history it is 
not just a matter of understanding documents but you also need to have a 
grasp of the literature and intellctual baggage of historians. I have 
often done work for archaeologists with my historians hat on but it is 
not without problems. Given a briefing meeting they will invariably list 
a number of wants which are very specific but  none of which are 
realsitic. I have to explain that it is probably contexualisng their 
site within the wider landscape and long-term economic and social 
patterns which is most effective and anything else is a bonus. Another 
problem i have is there is a tendency for archeologists at least in the 
UK to want everything eplained in tangible physical terms when 
jurisditial terms ued by historians e.g manor, feudal and borough are 
often not spatially tangible.When the documents do shed totally new 
light on the site their reaction can vary from grateful amazement to a 
sort of resentment. To give balance I have to say historians can be 
equally a a pain in different ways often by refusing to admit 
archaeological eveidence is of any value or refusing to read anything 
written by archaeologists- sorry mustn't get resentful here- no what the 
heck I am.  I have to say my pals (and enemies) are equally split 
between the two disciplines.