Aiden's skill tree is divided to four categories: Hacking, Combat, Crafted Items and Driving. These skills will make your jobs a lot easier and will get you through various situations. Learning skills will use up Skill Points. You can skill points by leveling up or completing certain side missions. Aiden can also learn Notoriety Skills. These skill will require points that you'll only get by completing online activities.
At the start of the game, you'll get the following skills:
You'll also start with 5 skill points. The tier 2 skills will be locked when you start the game. They will be unlocked during the campaign mission "Open Your World". You also need to get the skill in order. For example, Extra Battery I is needed before you can get Extra Battery II and III.
Get the Focus skill at the start of the game. This will allow you to slow time down, giving you a chance to land more accurate shots for easier kills or make precise, sharp turns when Driving. Focus regenerates over time but you can recover it instantly by using meds. You can also temporarily boost your Focus by ordering drinks from various cafes, bars and restaurants in the city.