Spoilers ahead:

This guide disregards gains through character creation; some traits give bonus attribute points!

Maximum in-game improvements:

• Strength (+2 permanent, +3-4 via equipment, +9 buffed)
• Perception (+2 permanent, +8 buffed)
• Endurance (+1 permanent, +7 buffed)
• Charisma (+2 permanent, +1 via equipment, +5 buffed)
• Intelligence (+3 permanent, +7 buffed)
• Agility (+1 permanent, +9 buffed)
• Luck (+4)

Notes:

• The max value for all primary stats is 10.
• All drug effects can be taken twice, and they all stack.
  • For example, taking Buffout (+2 strength) two times will give +4 strength. Taking Jet (+1 strength) two times will give +2 strength. Combined, you will get +6 strength from taking 2 Buffout and 2 Jet.
• All surgery enhancements require using a machine within a Brotherhood of Steel bunker in San Francisco. How to access the machine:

Strength (+2 permanent, +9 buffed)

+1 via surgery, +1 via perk, +3-4 via armor (while equipped), +1-6 via drugs (temporary)

A strength above 7 is usually unnecessary during character creation.

1. (+3-4 while equipped) Power armor:

   • T-51b Power Armor (+3)
   • Hardened Power Armor (+3)
   • Advanced Power Armor (+4)
   • Advanced Power Armor Mk II (+4)

2. (+1) Red Memory Module surgery. Where to find it:

3. (+1) Gain Strength perk

4. (+2 temporary) (+4 if taken twice) Buffout drug. Tip:

5. (+1 temporary) (+2 if taken twice) Jet drug

Perception (+2 permanent, +8 buffed)

+1 via surgery, +1 via perk, +1-6 via drugs (temporary)

1. (+1) Green Memory Module surgery. Where to find it:

2. (+1) Gain Perception perk

3. (+2 temporary) (+4 if taken twice) Mentats drug

4. (+1 temporary) (+2 if taken twice) Jet drug

Endurance (+1 permanent, +7 buffed)

+1 via perk, +3-6 via drugs (temporary)

1. (+1) Gain Endurance perk

2. (+3 temporary) (+6 if taken twice) Buffout drug

Charisma (+2 permanent, +5 buffed)

+1 via surgery, +1 via perk, +1 via item (while equipped), +1-2 via drugs (temporary)

1. (+1) Blue Memory Module surgery. Where to find it:

2. (+1) Gain Charisma perk

3. (+1 while equipped) Mirrored Shades when carried in an active item slot (the punch or kick slot). Where to find them:

4. (+1 temporary) (+2 if taken twice) Mentats drug

Intelligence (+2-3 permanent, +7 buffed)

+1 via surgery, +1 via story element, +1 via perk, +2-4 via drugs (temporary)

1. (+1) Yellow Memory Module surgery. Where to find it:

2. (+1) Hubologist zeta scan. How to get it:

3. (+1) Gain Intelligence perk

4. (+2 temporary) (+4 if taken twice) Mentats drug

Agility (+1 permanent, +9 buffed)

+1 via perk, +2-9 via drugs (temporary)

Every two points of agility give you 1 action point, so putting this to 10 (9 if you plan on eventually getting the perk) at the beginning of the game is a good way to go because having lots of action points is very useful. However, action points can also be gained through some other perks.

1. (+1) Gain Agility perk

2. (+2 temporary) (+4 if taken twice) Buffout drug

3. (+3 temporary) (+6 if taken twice) Psycho drug

Luck (+3-4 permanent)

+1 via perk, +1-2 via story elements, +1 via game encounter

1. (+1) Gain Luck perk

2. (+1-2) The Hubologist zeta scan. How to get it:

3. (+1) The Pariah dog. How to get it:

Bonus: in-game cheat for maxing all stats

There is a way to max all of your stats once you've finished the main quest: (though it is basically a cheat mode)

Perhaps the best walkthrough for Fallout 2 I have found, which includes all of these details and countless more: https://lemmings19.github.io/fallout-2-walkthrough/