As a Tomb King Player, I can recommend a couple things.
We have access to lore of Death, which will pop enemy heroes, which have poor leadership, quite nicely. Their leadership is por-to-average, so The Maw and Purple Sun are quite nice.
The Necrosphinx, with heroic killing blow, is scary, but not the end of the world. First he must hit, then he must roll a 6 to wound (or 5 if he's got Cursed Blades on him). The chance of him actually killing something outright is far from often (but if he's smart, he'll roll that attack first so that he can try to pop an ogre, then cause woundswith his remaining 4 attacks. Otherwise, he'll put a couple wounds on then kill off a wounded ogre.). As mentioned before, our ironblasters are quite capeable of handling all his monster threats.
Try to ignore basic skeletons, if possible. While it may be satisfying to crunch through 20+ models on the charge, he's likely to have another 30+ to hold you in combat for a while. If there's a hero in the unit, that changes things, making the unit more viable as a target.
Ushabti are both powerful and pointless at the same time. Essentially unbreakeable ironguts with ws 4 and i3, they come in at a rather-pricy 50 points a pop. I use ushabti as "road bumps" instead of combat threats, shooting at foes with great bows, then when charged, try to kill as many as possible before crumbling. However, that price tag keeps their unit size low, especially when you add the fact that Kings or Princes can't join them, like they can with Tomb Guard. Whack them with Leadbelchers or a firebelly, and try to avoid combat, as they'll strike first, hit more, and wound on average as a bull (Unless they're using Great Weapons, at which point they're likely to be flankers or a mainline unit)
Tomb Guard just scream "Shoot with leadbelchers and scraplaunchers" and those are the best ways to deal with them. While their killing blow won't affect our fatties, Tomb King heroes do more to buff Tomb Guard than any other unit in the army, other than maybe chariots. You're probably better off trying to kill as many guard in melee, but expect to get slaped around if a King and Necrotect are present. Ramhotep is even worse, not only providing Hatred to his unit, but also Frenzy. This, plus a prince, turns Tomb Guard into Warriors of Chaos with light armor. A king makes it worse, turning them into chosen with light armor.
The most common magic items in Tomb King armies are as follows: Glittering Scales, Golden Death Mask of Kharnut, Earthing Rod, Dragonhelm, Dragonbane Gem, Ironcurse Icon, Armor of Silvered Steel, and any ward save talisman.
Dragonhelm and Dragonbane gem are pretty straightforward in their purpose. The Golden Death Mask of Kharnut is the one you need to watch out for, not only bestowing Terror to the wearer, but also nullifying the General's leadership and the BSB's Hold Your Ground! special rules within 6 inches. Ogre leadership is poor, but with the negation of the General's leadership and BSB's rerolls, fear tests will the nerve-wracking, while they don't take any. Don't expect to win in a combat in which you fail a fear heck, as they're likely to capitalize on it heavily.