So, we're building a PHB1 Human Cleric. Gotcha. Others have done a pretty good job of laying the foundation, so let's go a little deeper.

Your main ability scores are going to be Strength, Wisdom, and Charisma, not necessarily in that order. This is going to mean a few things. Reflex will typically be your weak defense, whereas Fortitude and particularly Will should be really good. As an aside, one of the big differences in 4e is that the attacker always rolls. So whereas in other editions it might be a ranged attack roll to hit vs your static defense with a small ball of fire and a reactive roll to dodge vs a static attack against a big ball of fire, it's always a roll to attack vs a static defense regardless of the size of the fire.

Another thing your ability scores are going to influence is your choice in armor. Light armors (cloth, leather, hide, and their variants) add your Dex/Int bonus to AC. Heavy armors (chain being the one you start proficient in) do not. Given your likely lackluster Dex/Int, you'll probably switch to heavy armor if you don't start there from the beginning. Now, for a feat (and we'll cover that soon ... probably) you can use scale armor, but here's one of the interesting quirks you'll run into quite soon - magic weapons and armor are often restricted to certain types, so you may find that the cool class feature-boosting armor doesn't come in scale.

Beyond that, let's get to power choice. You're a human, so you get 3 At-Will powers to choose from.

Lance of Faith - Wisdom-based. Short range (close enough a dwarf could walk there in a single action). Deal some radiant damage (damage types are a common optimization route, but don't sweat it now) and give an ally a bonus to hit that target.

Priest's Shield - Strength based. Melee. Do some damage and give an ally an AC boost.

Righteous Brand - Strength based. Melee. Do some damage and give an ally an attack bonus vs that target.

Sacred Flame - Wisdom based. Short range. Bit of radiant damage and ally gets either Charisma based temp HP or a saving throw (which in 4e is a roll to shake off ongoing effects).

So you'll get a mix of melee and short range powers. You're going to stay up in the thick of things to reach your allies and your enemies.