Ranged Weapons:  This is a no brainer.  It increases your AS in ranged weapon attacks and it increases your DS.

Stalking and Hiding:  This skill lets you hide in the shadows unseen. This is important to archers because archers can fire bows from hiding and remain hidden. The sniping formula is unknown at this time, but the more you train in this skill the more you will be able to successfully snipe.

Perception:  Perception is the sole factor when aiming from the open, and when aiming from hiding it shares the role with ambush. In addition to aiming it also increases your ranged weapon AS after you have 40 ranks. The ranged weapon AS bonus is capped at 2x per training after 40 ranks. Perception also will provide you with a bonus to your DS.

Ambush:  Ambush helps you aim while hidden. Ambush also increases your ranged weapon AS after you have 40 ranks. The ranged weapon AS bonus is capped at 2x per training after 40 ranks. Ambush will also provide you with a bonus to your DS.

Dodging:  Dodging will improve your chances of avoiding an attack outright and it will give you a bonus to your DS. Training in this skill might save your life more than a few times.

Combat Maneuvers:  Training in combat maneuvers will give you access to the combat maneuvers list. Though maneuvers such as Shadow Mastery and Multi-Shot are not available yet, they will most likely be useful maneuvers to have. In the mean time, there are other maneuvers that you can train in that may be beneficial.