Beginner's Luck refers to a sliding hit chance increase for low-level characters that was added as part of Issue 12. Under Beginner's Luck, characters at Combat Level 1 have a base 90% chance to hit equal-level PvE enemies. This chance steadily decreases as the character gains levels and eventually reaches a steady 75% from Combat Level 20 onward. Prior to I12, the base chance for players to hit equal-level enemies was 75% at all levels.
Since Beginner's Luck is based on Combat Level, it is affected by Sidekicking and Exemplaring.