We have a SuperCheats.com exclusive game guide for Bioshock here:
http://www.supercheats.com/guides/bioshock/

There is a full walkthrough with screenshots and well as an overview of the game's weapons and enemies.

There is also a guide for all 122 Audio Diary Locations, Tonics list and weapons upgrade. All achievements are also listed.

Reaching Atlas Fontaine's Penthouse:
The code which is in an Audio Diary is 5744.

Hitting the Jackpot at Slot Machine:
Before you start playing the slot machine save the game and then keep reloading your saved game until you hit the jackpot.

Unlock Alternate Endings:
The ending you get depends on how the Little Sisters were treated during the game. The 'bad' ending will play if more than one Little Sister was harvested and the 'good' ending will play if no more than one Little Sister was harvested and the rest were rescued.

Complete the following tasks to get the corresponding GamerScore.

Upgraded a Weapon - GamerScore 5:
Get at least one weapon upgrade.

Basic Inventor - GamerScore 5:
Successfully Invent at least one item.

One Fully Upgraded Weapon - GamerScore 5:
Fully upgrade one weapon.

One Successful Hack - GamerScore 5:
Perform at least one successful hack.

Two Fully Upgraded Weapons - GamerScore 5:
Fully upgrade 2 weapons.

Prolific Photographer - GamerScore 5:
In every research group take at least one photo.

Researched a Splicer - GamerScore 5:
Take at least one Research Photo of a Splicer.

Bought One Slot - GamerScore 5:
In any Plasmid or Tonic track purchase one slot.

Lucky Winner - GamerScore 10:
Hit the jackpot at a slot machine.

Four Fully Upgraded Weapons - GamerScore 10:
Fully upgrade 4 weapons.

Fully Researched Bouncer - GamerScore 10:
Fully research the Bouncer.

Hacked a Vending Machine - GamerScore 10:
Successfully hack a vending machine.

Fully Researched Little Sister - GamerScore 10:
Fully research the Little Sister.

Fully Researched Nitro Splicer - GamerScore 10:
Fully research the Nitro Splicer.

Fully Researched Rosie - GamerScore 10:
Fully research the Rosie.

Fully Researched Spider Splicer - GamerScore 10:
Fully research the Spider Splicer.

Fully Researched Thug Splicer - GamerScore 10:
Fully research the Thuggish Splicer.

Three Fully Upgraded Weapons - GamerScore 10:
Fully upgrade 3 weapons.

Hacked a Safe - GamerScore 10:
Successfully hack a safe.

Toaster in the Tub - GamerScore 10:
Shock an enemy in the water.

Hacked a Security Bot - GamerScore 10:
Successfully hack a security bot.

Fully Researched Gun Splicer - GamerScore 10:
Fully research the Leadhead Splicer.

Fully Researched Houdini Splicer - GamerScore 10:
Fully research the Houdini Splicer.

Found Cohen's Room - GamerScore 10:
The player has entered Sander Cohen's personal quarters.

Irony - GamerScore 10:
The player has taken a picture of Sander Cohen's corpse.

Avid Inventor - GamerScore 10:
Successfully invent at least 100 items.

Five Fully Upgraded Weapons - GamerScore 10:
Fully upgrade five weapons.

Hacked a Security Camera - GamerScore 10:
Successfully hack a security camera.

Hacked a Turret - GamerScore 10:
Successfully hack a turret.

Completed Welcome - GamerScore 10:
Successfully complete the Welcome To Rapture Level.

Defeated Dr. Steinman - GamerScore 15:
The player has defeated the crazed Dr. Steinman.

Restored the Forest - GamerScore 15:
The player has restored the forests of Arcadia.

Defeated Peach Wilkins - GamerScore 15:
The player has defeated Peach Wilkins.

Weapon Specialist - GamerScore 20:
Acquire ALL upgrades for ALL weapons.

Maxed One Track - GamerScore 20:
Purchased every slot in one of the Plasmid or Tonic tracks.

Quality Research Photo - GamerScore 20:
Take a Research Photo of the highest grade.

Research PhD - GamerScore 20:
Max out ALL possible research.

Ammo Inventor - GamerScore 25:
Successfully invented ALL possible ammo types.

Became a Big Daddy - GamerScore 30:
The player has become a Big Daddy.

Defeated Andrew Ryan - GamerScore 30:
The player has defeated Andrew Ryan.

Broke Fontaine's Mind Control - GamerScore 30:
The player has broken Fontaine's mind control.

Completed Cohen's Masterpiece - GamerScore 30:
The player has completed Sander Cohen's great masterpiece.

Seriously Good At This - GamerScore 40:
Complete the game on the hardest difficulty setting.

Dealt with every Little Sister - GamerScore 40:
Either Harvest or Rescue every Little Sister in the game.

Skilled Hacker - GamerScore 40:
Successfully complete 50 hacks.

Historian - GamerScore 50:
Find every audio diary.

Maxed All Tracks - GamerScore 50:
Purchased every slot in ALL 4 Plasmid and Tonic tracks.

Tonic Collector - GamerScore 50:
Collect or Invent 53 Tonics in the Physical, Engineering and Combat tracks.

Little Sister Savior - GamerScore 100:
Complete the game without harvesting any Little Sisters.

Defeated Atlas - GamerScore 100:
The player has defeated Atlas.