Leveling in Fallout 76 is now more important than ever - you can get SCORE points by leveling and you need to scrap perk cards to get legendary perk coins.
WAYS TO GET % BONUS EXPERIENCE
100% from Lunchboxes.One lunchbox gives us 25%, but you can stack four of them to get 100%
25% from various food with Carnivore or Herbivore mutation and Strange in Numbers perk card.
Personally, i think that Herbivore food is easier to craft.
15% from level 3 perk card "Inspirational".
5% from Sleeping in your bed. There are three variants of this effect (1h/2h/3h).
5% from Booblehead: Leader. By default boobleheads' effects works only 1 hour, although you can expand it to 2 hours by using "Curator" perk card
5% from effect "Wisdom of Mothman" which you can get by interacting with Wise Mothman after finishing Event: The Path to Enlightenment.
5% from magazine Live & Love 8. Remember that it only works when in Team.
HOW INTELLIGENCE AFFECTS EXPERIENCE
A lot of research confirmed that INT in FO76 affects experience.
It turns out that experience math looks the same as Fallout 4 math:
Final XP = Base XP x( 1 + 0.03xINT )
WAYS TO GET BONUS INTELLIGENCE:
1. You can boost your INT by eating:
Chems also boost your INT, and the best INT boost chem are Berry Mentats
They last only 5 minutes but you can expand it to 12,5 minutes by using "Chem Fiend" perk card and BioCommMesh armor modification.
3. Be sure to always play in Casual Team which guarantees 4 INT.
4. Armor is also opportunity to get bonus INT.
Unyielding armor gives us +3 to all stats (except END) when we are on low health.
You can get additional 5 INT from armor's major legendary effect (1x5).
PATCH 20: HERBIVORE AND CARNIVORE MUTATIONS
After changes made in Patch 20, we can now get 2x effects from food.
Which means that e.g Cranberry Relish gives us 10% bonus XP without mutation.
Also, remember that "Strange in Numbers" perk card affects these mutations.