I don't put as much systematic thought into it, but I routinely restrict what classes and races I allow in my games.
My current game's lists are as follows (in spoiler blocks because of how long they are). Why the restriction? Well, some was to get the feel I was going for and some was admittedly just 'cause I'm ornery after 10 years of DMing 4e.
The players occasionally complain but they have also admitted that it makes character building simpler because they are forced to be more focused. Which I consider an intended consequence.
[sblock=Classes Allowed]
Class Source Allowed? Comments
Ardent Player's Handbook 3 NO no psionics
Artificer Eberron Player's Guide NO does not fit tone of campaign (too Steampunk-y)
Assassin Dragon Magazine 379 NO does not fit tone of campaign
Assassin (Executioner) Heroes of Shadow NO does not fit tone of campaign
Avenger Player's Handbook 2 yes this class will receive extra scrutiny to prevent abuse
Barbarian Player's Handbook 2 yes
Barbarian (Berserker) Heroes of the Feywild yes unclear how effective this class is, in practice
Bard Player's Handbook 2 yes mechanics are fine, but typical effete D&D bard is not - work with me
Bard (Skald) Heroes of the Feywild yes mechanics are fine, but typical effete D&D bard is not - work with me
Battlemind Player's Handbook 3 NO no psionics
Cleric (Templar) Multiple Sources yes
Cleric (Warpriest) Heroes of the Fallen Lands yes
Druid Player's Handbook 2 yes DM and player will work together to determine place in game
Druid (Protector) Heroes of the Feywild yes DM and player will work together to determine place in game
Druid (Sentinel) Heroes of the Forgotten Kingdoms yes DM and player will work together to determine place in game
Fighter (Knight) Heroes of the Fallen Lands yes remember that gimmick Charge builds are NOT allowed
Fighter (Slayer) Heroes of the Fallen Lands yes remember that gimmick Charge builds are NOT allowed
Fighter (Weaponmaster) Multiple Sources yes
Hybrids Player's Handbook 3, etc. NO prefer strongly archetypcal characters rather than hodgepodges
Invoker Player's Handbook 2 yes
Monk Player's Handbook 3 NO does not fit tone of campaign, and too fiddly
Paladin Player's Handbook yes
Paladin (Blackguard) Heroes of Shadow NO does not fit tone of campaign
Paladin (Cavalier) Heroes of the Forgotten Kingdoms NO no pets
Psion Player's Handbook 3 NO no psionics
Ranger Player's Handbook yes
Ranger (Hunter) Heroes of the Forgotten Kingdoms yes
Ranger (Scout) Heroes of the Forgotten Kingdoms yes
Rogue (Scoundrel) Multiple Sources yes
Rogue (Thief) Heroes of the Fallen Lands yes remember that gimmick Charge builds are NOT allowed
Runepriest Player's Handbook 3 yes
Seeker Player's Handbook 3 NO does not fit tone of campaign
Shaman Player's Handbook 2 NO no pets
Sorcerer Player's Handbook 2 yes
Sorcerer (Elementalist) Heroes of the Elemental Chaos yes this class will receive extra scrutiny to prevent abuse
Swordmage Forgotten Realms Player's Guide yes
Vampire Heroes of Shadow NO does not fit tone of campaign
Warden Player's Handbook 2 yes DM and player will work together to determine place in game
Warlock Multiple Sources yes
Warlock (Binder) Heroes of Shadow NO mechanically terrible
Warlock (Hexblade) Heroes of the Forgotten Kingdoms NO no pets
Warlord (Marshal) Multiple Sources yes
Wizard (Arcanist) Multiple Sources yes
Wizard (Bladesinger) Neverwinter Campaign Setting yes this class will receive extra scrutiny to prevent abuse
Wizard (Mage) Heroes of the Fallen Lands yes this class will receive extra scrutiny to prevent abuse
Wizard (Sha’ir) Heroes of the Elemental Chaos NO does not fit tone of campaign, and mechanically terrible
Wizard (Witch) Heroes of the Feywild NO does not fit tone of campaign, and mechanically terrible[/sblock]
[sblock=Races Allowed]
Race Source Allowed? Comments
Bladeling Dragon Magazine 419, Manual of the Planes yes
Bozak Draconian Dragon Magazine 421 NO does not fit tone of campaign
Bugbear Monster Manual NO oversized weapons create too many rules problems
Bullywug Monster Manual 2 NO does not fit tone of campaign
Changeling Eberron Player's Guide NO rules and role-playing nightmare
Deva Player's Handbook 2 yes
Dragonborn Player's Handbook yes Dragonfear racial power is NOT allowed
Drow Forgotten Realms Player's Guide yes
Duergar Monster Manual 2 NO does not fit tone of campaign
Dwarf Player's Handbook yes
Eladrin Player's Handbook yes
Elf Player's Handbook yes
Genasi Forgotten Realms Player's Guide yes
Githyanki Monster Manual yes have a specific niche within the story - work with me
Githzerai Player's Handbook 3 yes
Gnoll Dragon Magazine 367 NO prefer to avoid monstrous races
Gnome Player's Handbook 2 NO DM intensely dislikes this race
Goblin Monster Manual, Into the Unknown: The Dungeon Survival Handbook NO does not fit tone of campaign
Gold Dwarf Neverwinter Campaign Setting yes
Goliath Player's Handbook 2 yes
Half-Elf Player's Handbook yes
Halfling Player's Handbook NO DM intensely dislikes this race
Half-Orc Player's Handbook 2 yes remember that gimmick Charge builds are NOT allowed
Hamadryad Heroes of the Feywild NO does not fit tone of campaign (too twee)
Hengeyokai Dragon Magazine 404 NO does not fit tone of campaign (too twee)
Hobgoblin Dragon Magazine 419, Monster Manual yes this race will receive extra scrutiny to prevent abuse
Human Player's Handbook yes
Kalashtar Eberron Player's Guide NO does not fit tone of campaign
Kapak Draconian Dragon Magazine 421 NO does not fit tone of campaign
Kenku Dragon Magazine 411, Monster Manual 2 NO does not fit tone of campaign
Kobold Monster Manual, Into the Unknown: The Dungeon Survival Handbook NO does not fit tone of campaign
Llewyrr Elf Dragon Magazine 405 yes
Longtooth Shifter Player's Handbook 2 NO does not fit tone of campaign
Minotaur Player's Handbook 3 yes
Moon Elf (Eladrin) Neverwinter Campaign Setting yes
Mul Dark Sun Campaign Setting yes this race will receive extra scrutiny to prevent abuse
Orc Monster Manual yes remember that gimmick Charge builds are NOT allowed
Pixie Heroes of the Feywild NO DM intensely dislikes this race
Razorclaw Shifter Player's Handbook 2 NO does not fit tone of campaign
Revenant Multiple Sources NO does not fit tone of campaign
Satyr Heroes of the Feywild NO does not fit tone of campaign
Shadar-kai Dragon Magazine 372 NO does not fit tone of campaign
Shade Heroes of Shadow NO does not fit tone of campaign
Shardmind Player's Handbook 3 NO does not fit tone of campaign
Shield Dwarf Neverwinter Campaign Setting yes
Sun Elf (Eladrin) Neverwinter Campaign Setting yes
Svirfneblin Into the Unknown: The Dungeon Survival Handbook NO DM intensely dislikes this race
Thri-Kreen Dark Sun Campaign Setting NO prefer to avoid monstrous races (and Russ isn't playing)
Tiefling Player's Handbook yes don't make me regret this, again
Tinker Gnome Dragon Magazine 422 NO DM intensely dislikes this race
Vryloka Heroes of Shadow NO does not fit tone of campaign
Warforged Eberron Player's Guide NO does not fit tone of campaign
Wild Elf Neverwinter Campaign Setting yes
Wilden Player's Handbook 3 NO does not fit tone of campaign
Wood Elf Neverwinter Campaign Setting yes [/sblock]