This time we have Nate, a pokemon convert wanting some advice on a black/blue control deck.  Nate, welcome to the light side, we're glad to have you.
Here is the primary decklist, which, Nate explains, focuses on "counterspell/creature destruction."

>Creatures:
>3 Plague Spitters
>2 Thrashing Wumpus
>3 Glacial Wall
>2 Air Elemental

>Land:
>4 Salt Marsh
>8 Swamp
>10 Island

>Other:
>4 Brainstorm
>4 Accumulated Knowledge
>4 Undermine
>4 Counterspell
>4 Spite/Malice
>4 Recoil
>4 Dark Ritual

>Side Board:
>2 Avatar Of Woe
>4 Cremate
>4 Perish
>2 Tsabo's Decree
>2 Planeswalker's Scorn

         So, at first look, a couple of things.  The deck is very much a control deck, and so, should utilize a higher land count, say 25, and would certainly not be hurt by the use of the black/blue pain lands from 6th edition, Underground River.  Since the decks bulk of double casting cost spells(either BB or UU)lie in blue, with air elemental, undermine, and counterspell, there should probably be 4 salt marsh, 4 Underground rivers, 9 island, and 8 swamp.  This won't rule out mana troubles, but it'll certainly help the situation. 
         Onto the creatures.  I've found that Plague Spitter is phenomenal against both fires' early creatures as well as some of the rebel searching engine.  As an added bonus, if the spitter dies on your turn, he takes down half of a mono-white rebel decks creature force with him(if there are no crusades in play, you should be able to arrange that).  However, 2 is probably all we need.  We'll also increase the number of thrashing wumpuses to 3.  The wumpus not only controls the board and takes out most creatures, he also attacks for a healthy sum, and is as good at taking out opponents with his ability as he is creatures.  I also have no problems with glacial walls holding the fort against blastoderms and Air Elementals ruling the sky in pairs. What I'll also do is add two crypt angels, for two reasons.  One: they recycle your walls and elementals, and two: they're pro-white beat sticks!!  What's not to love?!!  You're batting 1000 so far Nat, lets see if you can keep the streak alive.
         Now the spells.  Since we've upped the land count, brainstorm loses its utility power and Fact or Fiction(FoF to his friends) steps up to the plate to replace it, and it does a fantastic job.  In a control deck, card advantage can make or break the game, and nothing says card adantage like our old friend, FoF.  Not to mention accumulated knowledge is best buddies with FoF.  Discarding a knowledge to FoF doesn't bother us at all, because when the next one comes, we'll draw the card for the previous one too.  We really like having it in our graveyards, so what if our opponent helps get it there?  So, 2 FoFs it is.  And we'll keep all 4 Accumulate knowledges, we like them way too much, now that FoFs are in.  We'll also keep all of the recoils, counterspells, undermines, and dark rituals, because they all do their job very well.  A small note here though, undermines are highly suspect for a control deck where the game is won through controlling the board and answering all of your opponents threats, rather than by doing small increments of damage every now and then.  Oh well, they are still a counterspell, and without a better substitute, they stay.  Spite/malice, however, is on the edge, and I think I'll just push it off.  We'll replace spite/malice with 3 washout and 2 yawgmoth's agenda.  The washouts are really good against a lot of decks, and they buy you a great deal more time than a spite malice in the fight to stay alive against aggressive creature decks.  How much time does washout buy when the fires opponent returns not only their mana creatures but also all of their other creatures AND their fires of yavimaya?  A lot my friend, a lot.  Same goes for rebels and all of their stupid white permanents, counters or no.  As far as Yawgmoth's agenda is concerned, I cannot say enough.  Late in the game, when your hand is low, or when you need that one card to give you the momentum back, agenda is it.  This card can singlehandedly win the game for you if you any sort of significant graveyard.  Card drawers and counterspells only feel better used the second time around.  There's also something to be said for the opponent at three life and you with agenda, 2 blue and a black available, and an undermine in the grave.  Some good that. 
         Finally, the sideboard.  A little disclaimer.  I assume fires and rebels/counter rebels are the most popular decktypes, so I'll look at the sideboard from that aspect.  Here's the sideboard:

4 Perish-rarely a bad card with fires, and occasionally blasto-geddon
3 Cremate-zombies, spirits, hammers, oh my!
2 Massacre-quicker than decree, good against straight white, and free, so why not?  Also helps prevent geddons.  No creatures means white doesn't geddon.
2 Tsabos Decree-good against all rebels, decree is to rebels what Raid is to roaches.  Rebels are even kinda like roaches...really.
4 Gainsay-lotsa blue around in mono-blue, counter-rebels, and both white/blue and black/blue control, in an environment where red is prevalent, which it doesn't seem to be, chill is the outright better hoser card, but people seem to hate decks that are predominantly red, so Gainsay it is.  Here's our final deck:

Land:
4 Slat Marsh
4 Underground River
9 Island
8 Swamp

Creatures:
2 Plague Spitter
3 Thrashing Wumpus
3 Glacial Wall
2 Air Elementals
2 Crypt Angel

Spells:
4 Recoil
4 Dark Ritual
4 Counterspell
4 Undermine
2 Fact or Fiction(FoF!)
3 Washout
2 Yawgmoth's Agenda

Sideboard:
4 Perish
4 Gainsay
3 Cremate
2 Massacre
2 Tsabos Decree

There ya go Nate, hope I helped more than I hurt, until next time, keep killing those roach-like rebels,
-Wally West