The following is a very brief and old tactics summary from about the year 2000! I don't actually think I've played with my High Elves much more since then.
I don't really have any tactics as such. I mainly play in Bring and Battles at GW Bolton. In a Bring and Battle tactics are burnt and all ideas of an even fight are destroyed. It's do or die time!
High Elves may be expensive but, if in the right conditions (i.e. not being charged by heavy cavalry, Chaos warriors and definitely not Chaos knights) the can more than hold their own, sometimes against the odds. For this reason I try to get my spearmen into combat as quick as possible. Moving them forwards also stops people from engaging your archers and Bolt Throwers in combat if your spearmen flee.
While your spearmen advance, your cavalry can advance just behind them. Their larger move means that the can hang back, and so not get charged by much, and still charge along with the spearmen.
Your archers and Bolt Throwers have the easiest job. All that they have to do is sit at the back of your army and shoot at :-
This is simple, as the High Elves have the strongest and best magic in the game it is obvious that you MUST keep Fiery Convocation and Assault of Stone if you get them. Banishment is priceless against Chaos and Undead. It is especially nasty if combined with the 24" move from Coruscation of Finreir.
If you haven't worked it out by now, High Elves can kill most things in combat, shoot it to death or blast it to kingdom come with magic. The only problem is that they are very expensive.
Hive World Terra