I could write reams on the best tactics for WE... or other armies for that matter, and I am by no means a tourney winning gamer. Also, I find the best tactics vary from opponent to opponent, and army to army. This variability to some extent explains why white dwarf tactics articles tend to be shallow and a tad pointless.
However, you raise a question fundamental to our enjoyment of collecting, painting and pushing our hundreds of little toy soldiers around a table. I will comment in broad strokes as I would be here all day trying to cover all bases, when I play I plan and strategise in terms of function of units rather than worrying so much about specific tricks/magic items/special traits - unless those are integral to the function of a unit, and I also have a proverbial [insert expletive of choice here] load of work to do today so can only procrastinate for a little while...
The main opponents I face are:
Empire - an almost perfectly balanced traditional GW empire army commanded by the resident champ gamer in my circles... only with mortars instead of the more usual cannon (I have developed a nervous tick in response to what those mortars can do to line infantry)
Skaven (erratic special rules driven vermin!)
Very occasionally orcs/goblins
As such, my tactics should be viewed as limited by the traits of what I use them against.
In broad strokes I employ:
Cover and concealment wherever possible - our troops are too expensive to suffer attrition unecessarily, and mostly too fragile to tough it out.
Movement! Use it - keep the other person guessing, redistribute the weight of your forces unexpectedly - puts their plans and battle line in disarray, can leave them charging into a void and enable you to stack on a more vulnerable point. Few armies can match WE for this, so practice it, experiment, do the occasional crazy mnove and see what opportunities for mischief it opens up. If you are facing a slow enough opponent, move forward to get in close range and shoot, then back off - lure them into a trap etc.
Denial of areas through either concentrated shooting (only works against some forces - others will just charge through) of putting dryads/wardancers in forrests where they are too hard to dislodge, but can charge out into the flanks of unwary units as they move past.
Hammer and anvil - Treeman/Lord and EG as anvil... I personally struggle to decisively win combats without an anvil of some sort... there are other units that can serve for this as well, but the key is to have them able to survive the shooting and magic phases (usually by hiding) followed by at least one turn of melee unsupported. If the unit can't do this, it isn't an anvil. Anything that dishes out LOTS of wounds will do for the hammer.
Swarming - this is when you spread out your forces, then have them converge on a point. Movement 10 on the march and the easy reform of skirmishing units enables some unexpected flexibility with this tactic. Ideally, the enemy closes on a unit that looks exposed/ unsupported (an anvil is best, as that unit may need to withstand a charge and stick around) but then a greater number of units than expected hit the charging enemy in the flanks. I have had success with this against ogres and bretonians - not so much with Empire due to the sheer number of blocks of troops and the particular tactics that player (Paladin) usually employs. This type of tactic is employed in modern armies also - esp. in A-symetric warfare... not that I'm convinced real world tactics are ever reflected in toy soldier games... Use in conjunction with denial of territory, hammer and anvil and cover and concealment.
Target priotity. Important for any army, but WE especially... I generally try to knock ranks off of lighter armoured ranked units. Concentrate on one unit as long as you can and remove that element from their battle line... makes it easier to swarm, survive hammer and anvil without being counter charged etc. Don't wast your time on heavy cav unless they are small isolated units or there is nothing else to shoot at - cav can be better dealt with by dragons, treemen, flank charges, pre-emptive charges etc.
Keep the initiative - charge first whenever you can with melee units - even archers if you know shooting is not going to be decisive that turn.
Archers are a melee unit. I used to field units of 10, kept them mobile and shooting... this works ok against some opponents but not against anything with a combination of heavy cavalry and ranked units, or cheap ranked units... tends to result in running out of places to run to and either fleeing, or being disadvantaged in combat. I now field blocks of 18 or so in 3 ranks of 6. Small enough to keep manouvreable, but big enough to flank charge into melee and have still have >10 models after return attacks in order to disrupt the opponent/ remove their rank bonus. I recently played against a hord of HE archers... they proved much more resilient than I had thought. Remember, historically English longbowmen were expected to engage in the melee once the enemy had closed. Pitching GG into combat might seem like a waste of points, but then, so is doing nothing with them once the shooting has become less important and the melee is the main game decider.
attacking war machines - shoot em if you have to, getting into combat in the back line is better. Skilled players generally make it very difficult to get to their war machines. However, the points/troops they invest in a war machine body guard to stop the occasional 50pt eagle from getting in amongst their soft back line are points/troops not contributing to the main game winning melee. If getting to the war machines/back line is critical, employ multiple small units that move fast - GR, WE, WHR, characters on flying mounts, even infiltrating scouts/WW or WR... then apply the swarm tactic - too many targets means they won't stop them all, the more they try the less they are investing in your hammer and anvil, and the ones that get there will still be dangerous. Accept that this changes the game dynamic and you will suffer casualties, so calculate the cost/benefit analysis of getitng through the war machine body guard. I find it is less about the points value of what you are killing/ what you invest to kill them and more about the effect war machines have on the core functions of your army.
Monstors! In larger games I use the WE dragon with a melee focused lord. Fill a gap in my tactics and battle line - it is both hammer and anvil and can employ the swarm tactic. There are now so many monstors in the game it's getting a tad silly, but for WE a dragon and a treeman or two is in character... just make sure you give em enough protection! Especially against montrous killing blow (I'm looking at you, Mr Bretonian), cannon, magic and the like. If you can get them to survive, they will dish out enough damage with great weapons and 'natural' attributes to be worth taking. I usually max out on ward saves and armour.
Magic - I used to play Dwarfs, so I'm not a huge magic fan... however I usually take a L4 mage - more useful than a combat Lord. Personally, I find Mages are more useful for augmenting combat units to keep our fragil troops fighting fit and in the melee... as well as stopping enemy spells from disrupting my plans. WE are particularly vulnerable to loosing a key unit, or being stopped from making a key move for a turn, as we are points expensive and rely on manouvreability for most tactics. As such, more defensive magic often gets a better return for points investment and has more influence on game outcome (albeit less obviously). I find Dwellers and such like unsporting and some of my friends, like many gamers, have banned that and similar spells from our games. Some WE players use cunning stuff like moonstone of the hidden ways, but try as I might I have never got this to work. Good luck to you if you can.
There's more, but I just looked at the size of my post, so kudos if you bothered to read this far.
Good luck killing the other guy.