Collect all artifacts: See "This... this is history..."
Find and purchase all parcels: See " Your mail is on your desk"
Get "True Adventurer" rank on all levels: In each level, at the top of the screen you'll see a Lego bar that fills up as you collect more studs. This bar needs to get filled up in each level, and is much easier to do with the multipliers turned on.
Unlock All Characters: See " You chose... wisely"
Complete all levels, including all story missions, plus the three hidden levels:
To unlock the hidden levels, go to Indy's office, which is in the college off the main hallway. Go there once you have unlocked each type of character. Use each character's ability in there and collect the chests to the middle of the room. Build a new chest and retrieve the key. Then take the key up to the artifact room, and use it in the crank created by following the steps in "Got lost in his own museum." Surrounding the crank will be 3 grated holes, each the opening for the hidden levels. In order to unlock the levels:
Young Indy: Collect all artifacts in "Raiders of the Lost Ark"
Ancient City: Collect all artifacts in "Temple of Doom" (Guide)
Warehouse: Collect all artifacts in "The Last Crusade"
Warehouse Tips: Enter the level as a bazooka character, and run as far to the right as you can. You will eventually see a target, shoot it with your character and it will drop an unlimited amount of studs. Repeat until 1,000,000 is reached.
1. There has been a report that this Lego game has the same 100% glitch as did Lego Star Wars: TCS, basically, the game shows you at 100%, but no achievement. The solution that worked in the first game, works on this incarnation as well. Exit from the game completely, and go back to the dashboard. Then boot the game back up, go into any level at random, and then save and exit the level, and the achievement will unlock.
2. For some people, the requirements for Young Indy and the Ancient City are reversed, and collecting all the artifacts in Raiders will unlock the Ancient City instead. So be advised that this may happen to you, so don't be alarmed.