This is a great thread, hope other players post as this was one of the posts I was going to make as a fairly new 6 month AoS player it can be impossible to formulate a tactic against a army you havn't played against a few times.
I played against Fyreslayers last week. Lost terribly which isn't a problem. The run down as we set up was "fyreslayer troops attack first and attack twice. Negate magic on 4+, and save after save of 4+". I figured as an alpha strike army avoid his tight pile of 3 troop units of 5,10 and 10 and 2 heros on one objective and go for the large 30 single unit with hero as at least only have 2 attacks against me rather than 4-5 before I get to even attack.
Afterwards with a bit of homework I realise only 1 unit can attack twice and attack first with command point spend (his big unit), the negate magic actually is a priest artefact with 12" range and save after save is also a limited area buff. (Im right thinking an army can only have one copy of an artefact?) I don't have battletome to check. So I figure next time, I'll know to ask which hearthguard bezerkers are part of battalion as that's the unit to avoid, not attack!!!
So summarising your army, what do people recommend? Brief can be unhelpful as above to new players and it natural not to reveal major weaknesses but then newbies make quite glaring errors from the off. My main concern is not trying to win but by losing so easily, players wont want to replay again as I provided no fun or challenge at all.
How much detail should we go into and how many questions are appropriate when trying to really understand your opponents army synergies?
Do keep posting as is a really helpful thread.