Skills are split into Basic, Trained, and Expert difficulties. Basic and Trained Skills are based off a primary Attribute plus the Bonus of a secondary Attribute. Expert Skills are extremely difficult being based off the Bonuses of two Attributes. Listed below are all the skills by category and their base score.

Final Skill value is Primary Attribute (or Bonus) + Secondary Attribute Bonus + (1d3/1d5/or 2d5 keep highest + advancement bonus)/ skill rank added. For example, a character with a 27 Strength and a 30 Perception tries to swing a bat. The base skill would be 27 + 3 = 30. Without any special aptitude from Abilities, the skill would go up 1d3 per skill rank. On the other hands lets say they have Athletic Conditioning (Baseball) 3 which Supports and gives an Advancement Bonus to Melee Attack Bludgeoning. The base skill would be the same but each skill rank would add 1d5 +3.

Basic
Balance Per + Ws
Brawl Str + Pb
Climb Str + Wb
Composure Will + Eb
Dodge Per + Sb
Endurance Str + Wb
Expression Emp + Pb
Grapple Str + Wb
Hold Wll + Pb
Jump/Leap Str + Pb
Lift/Pull Str + Wb
Resist Pain Wll + Sb
Search Per + Wb
Spot/Listen Per + Wb
Stealth Per + Wb

Trained
Bow/Crossbow Per + Sb
Calm Other Emp + Wb
Diplomacy Barter/Bribe Emp + Wb
Diplomacy Command/Coax Emp + Wb
Diplomacy Determine Motives Emp + Pb
Diplomacy Intimidate Emp + Sb
Diplomacy Persuade Emp + Pb
Digital Systems Per + Wb
Firearms Long Gun Per + Wb
Firearms Pistol Per + Wb
First Aid Per + Wb
Melee Attack Bludgeoning Str + Pb
Melee Attack Piercing Str + Pb
Melee Attack Slashing Str + Pb
Navigation Per + Wb
Swim Str + Wb
Throw Per + Sb

Expert
Advanced Medicine Pb + Wb
Craft/Construct/Engineer Pb + Wb
Martial Arts Sb + Pb
Pilot Pb + Wb
Ride Eb + Wb
Science Pb + Wb
Survival Pb + Wb
Toughness Sb + Wb