The following mastery setup is a good general setup for any attack damage carry in the game. The Tier conditions are not known yet. In this guide i assume that they won't be changed, so summoners have to spend at least 4/8/12/16/20 points unlock Tier 2/3/4/5/6 respectively.

Offense Tree

Tier 1

The following mastery setup is a good general setup for any attack damage carry in the game. The Tier conditions are not known yet. In this guide i assume that they won't be changed, so summoners have to spend at least 4/8/12/16/20 points unlock Tier 2/3/4/5/6 respectively.

Offense Tree

Tier 1

• Summoner's Wrath, 1 point: Most carries run ignite or exhaust so improving them is a good idea.
• Brute Force, 3 points: This means +3 damage, which is better than the other possibilities in this tier.

Tier 2

• Alacrity, 4 points: 6% attack speed bonus. Attack speed is very useful on all attack damage carries.

Tier 3

• Deadliness, 4 points: +4% critical strike chance. Most AD carries use critical strike, so this little boost can give some advantage especially on low level.
• Weapon Expertise, 1 point: +10% armor penetration. This really worth the point in my opinion, because most attack damage carries use armor penetration runes.

Tier 4

• Lethality, 1 point: 10% critical strike damage.
  
  Worth the point.
• Vampirism, 3 points: 3% lifesteal. Better sustain, can help the laning phase.

Tier 5

• Sunder, 3 points: +6 armor penetration.

Tier 6

• Executioner, 1 point: +6% damage to targets below 40% health. This is pretty good for all carries. Produces better ganking ability and easier minion last hitting.

This can be the typical AD carry build in my opinion. I can think of one variation though. If your champion doesn't benefit of critical strike that much, then on Tier 3 invest 3 points in Havoc for 1.5% increased damage and leave Deadliness with 2 points(please note that you won't have Lethality this way). So far we have spent 21 points. Use the rest on the Utility tree.

Utility Tree

Tier 1

• Summoner's Insight, 1 point: Well i doubt that Flash can be nerfed that much it won't get selected by most carries, because this is the only decent gap closer/escape spell.
• Expanded Mind, 3 points: 12 mana/energy per level. Gives slightly larger pool to use abilities.

Tier 2

• Swiftness, 4 points: 2% movement speed bonus. All champions can make use of this, faster movement can help early ganks.

Or

• Swiftness, 1 point: 0.5% movement speed bonus.
• Meditation, 3 points: +3 mana regen per 5 seconds. If your carry is mana based, then this option can be used.

Tier 3

• Runic Affinity, 1 point: 20% longer buffs duration. Buffs play very important role in the game, so the longer they last the better.

I think this setup is pretty good for attack damage carries and will be used by lot of summoners. It gives attack damage, attack speed, armor penetration and life steal. So generally more damage.