I've previously said that for book research I prefer to trust original ancient sources over modern ones, but there's one field where I would never dare to question the modern experts, and that's the people who are into military re-enactment. I don't think there's anyone more into getting details right than these guys.
You've probably heard of the Society for Creative Anachronism. SCA is more mediaeval than ancient, though it does have its ancient enthusiasts. SCA covers all the aspects of past times, but anyone who's ever been to a SCA festival could tell you it's the skirmish combats that get the crowds.
There are similar re-enactment groups who're more ancient oriented, though the organisations don't seem to be as closely knit so if you're interested you'd need to google around for what's in your area. Most of them are into Roman army reconstruction but there are some Greek Hoplite groups too.
A good place to start would be Ancient Warfare Magazine. I'm pretty sure most of the people who write or read it are into doing re-enactments. (No, I don't do this myself, but it's fun to watch.)
Despite its name, the Roman Army Talk forum has a substantial Greek section. These guys are awesome for minute details about how people used to slaughter each other. If you want the pros and cons of holding your spear overhand vs underhand, then this is the place to be. Their knowledge of military history would rival that of any Oxford don.
I don't need this sort of information very often, because Nico's not into regular army life. When he gets into a fight, it's invariably a street brawl in some grotty back alley, or else a tavern brawl (I had such fun writing the barroom fight in Ionia Sanction).
But when I do need soldierly detail, the re-enactors have the advantage that they've actually tried out in real life the stuff that's mentioned in original sources. They bring a certain practicality to the subject that makes it easier to sort out from the original sources what's likely true and what might be false.