This is very crucial. You GOTTA know how to sideboard.
What i like to do, and i recommend you folks to do, is consider what creatures are effective against your opponent. Plus, ditch Sire Of Insanity on most games.
Sire of Insanity is an awesome card. It wins games if you pull it on Turn-1, 2 and sometimes 3... But on the other games, it is VERY likely that you won't be able to pull it that fast, after all.. Grave-Hate is a bitch...
Also, If they are using any sort of combination that might cast Abrupt Decay, then it is better to drop Animate Dead.
If they are on a very aggro build, like Burn... you can throw away Reanimate in order not to give yourself a faster clock.
If, by any means, you are facing something like another Reanimator, Dredge... or an opponent which you don't want his creatures coming back to life, then it's better to leave a few Exhumes behind.
Usually i do a more control-ish build on the second and third games. I ditch a bit of the reanimation based on the opponent's deck, I ditch some of the creatures that won't have any impact on the game, and i also ditch Gitaxian Probes, maybe one Dark Ritual.
Then, I bring in as much disruption as I can find. So i can break their hands, together with Abrupt Decay and Stronghold Gambit.
Usually Pyroclasm goes against Death and Taxes, Goblins... And I put 1 copy against Grixis Pyromancer, UW Mentor and Delvers just in case.
Pithing Needles are good against Karakas, Deathrite Shaman, Grindstone, Liliana of the Veil, Sneak Attack and THE LOCK (Counterbalance + Sensei's Divining Top
).
Against Enchantress i like to go Back to Nature because their Leyline of Sanctity totally busts our discard spells... And they run Rest in Peace in the maindeck. Also, you may run Reverent Silence which is basicly the same.
Against Dredge and other Reanimators, I also like Tormod's Crypt or Extirpate (the later one because we don't run counterspells to guarantee Surgical Extraction will resolve).
Defense Grid is good-ish... I like it because it protects your combo... I dislike it because it may backfire... A LOT... sometimes you have to Decay your opponent at instant speed in the end of their turns, but you can't.
Ratchet Bomb or Powder Keg are useful against BUG Delver and other decks with a lot of 1/2 drops... Because most of their Grave-Hate is also a 1/2 drop.