Here is how optimization works in 4.0: it doesn't. As long as you do something reasonable, you won't be that far off from the best possible when it comes to making your character. There are a few broken combinations, but they are way broken and it's obvious how to nerf them so that they are fair. Here is how to make a good character: a bad character won't be that far behind, as long as the character's primary attack stat is okay.
1) Pick a role that you want to fill, and come up with a rough character concept.
2) Pick a class that goes along with that role and concept.
3) Look over the feats that you will eventually want to take. Note the ability score prerequisites for each. Paladins, Fighters, Warlords, and to a certain extent Wizards need to be careful here.
4) Set your ability scores, making sure that you have at least a 16 in your primary attack score and that you will eventually qualify for the feats you want (weapon and armor specialization are the most exacting). Choose a race that help you here: +2 to your primary attack ability is ideal, but there are other factors. Human is always a good choice.
5) Pick your powers/exploits so that they work with your weapon/ability score setup. Chose reasonable feats. Durable, Toughness, and Improved Initiative are all good, as are the appropriate focus-type feats.
6) Pick starting equipment. Just take the most effective stuff that your class lets you use.
Race rank by class
Cleric
1) Elf
2) Dwarf, Human
3) Dragonborn
Fighter
1) Dragonborn
2) Human
3) Elf, Halfling, Dwarf
Paladin
1) Dragonborn
2) Dwarf
3) Human, Elf
Ranger
1) Elf
2) Human
3) Dwarf, Eladrin
Rogue
1) Halfling
2) Elf
3) Eladrin, Human
Warlock
1) Tiefling, Half-elf
2) Human
3) Halfling, Dragonborn
Warlord
1) Dragonborn
2) Human
3) Eladrin, Tiefling
Wizard
1) Human
2) Elf, Eladrin
3) Tiefling
Note: this ranking is according to my opinion, and with each class, what works with one race may not work with another. This is especially true for the Fighter and Paladin classes, where choice of weapon and play style need to be considered together.
Multiclassing:
If you want to do it, pick a second class that has some synergy with your primary class. A rogue multiclassing as a warlock with a pact blade makes sense both thematically and in terms of game mechanics, while a paladin multiclassing as a wizard does not.
Character builds you may not have thought of:
Lu Bu: An Elf Fighter who runs around with a glaive, pushing around anyone who comes near him.
John Henry: A Dragonborn Fighter with a maul, who just pounds people. A one-trick pony.
Abrams: A Dwarf Fighter with a warhammer and shield, focused on defense.
Hexhammer: A Half-Elf Warlock/Fighter, who curses as he smashes.
Lite Brite: An Elf Cleric who zaps foes with holy light.
The Controller: An Elf Wizard with high Wisdom, an orb, etc.
