Athletics skill is a new skill under DR 3.0 that combines Climbing and Swimming, as well as some aspects of Escaping.

Athletics is a survival skill that measures your ability to move through bodies of water under your own power and climb obstacles.

Spells and abilities that boost Athletics

Spells and abilities that decrease Athletics

None

For training locations, see Climbing and Swimming list
Dancing rope item.
Windboard item.
Breaking and Entering entry holding a climbing rope such as a braided or store bought heavy rope

Things that help boost Athlectics skill:

Appraising an obstacle before attempting the climb helps based on your success at appraising. Note that appraisal difficulties are currently inaccurate, but will still help with the climbing attempt.
Being led by a superior climber increases climbing ability. Being led by a superior climbing Ranger increases it even more.
Ranger wilderness bonus
Thief - Thief confidence and Urban bonus both include Climbing, per GM-Risek, post #7425 in The Den, A place to talk, squeal, "You can definitely boost your escaping skill with khri. You can boost it by a great deal. You don't have a specific ability to boost you climbing, but it is covered under your Urban Bonus and in Confidence."
The role of stats in climbing has been increased. Both agility and strength will aid in climbing, so any other ability that boosts agility and/or strength helps as well.
Lack of current in a body of water
Lack of encumbrance, armor hindrance, and injuries also play a role.