Complete ''Greatest Kingdom in Middle-earth'
just Complete the first level.

Complete ''An Unexpected Party''
just Complete the second level.

Complete ''Azog the Defiler''
just Complete the third level.

Complete ''Roast Mutton''
just Complete the fourth level.

Complete ''The Troll Hoard''
just Complete the fifth level.

Complete ''Over Hill and Under Hill''
just Complete the sixth level.

Complete ''Goblin Town''
just Complete the seventh level.

Complete ''Out of the Frying Pan…''
just Complete the eighth level.

Complete ''Queer Lodgings''
just Complete the ninth level.

Complete ''Flies and Spiders''
just Complete the tenth level.

Complete ''Barrels Out of Bond''
just Complete the eleventh level.

Complete ''A Warm Welcome''
just Complete the twelfth level.

Complete ''Looking for Proof''
just Complete the thirteenth level.

Complete ''The Necromancer''
just Complete the fourteenth level.

Complete ''On the Doorstep''
just Complete the fifteenth level.

Complete ''Inside Information''
just Complete the sixteenth level.

Collect 99 of any loot
Woods, Leathers, Ropes and Stones are very common.

Obtain 150,000 studs from Instruction Builds bonuses. (Single Player Only)
Each level have Instruction Build so you can get this through stoty.

Play a level in co-op
You don't need a friend, just presst F2 to enter into co-op and complete a level.

Create a custom character.
In the lake-town, Esgaroth, you have Charaster Customizer.

Transform to Beorn's bear form.
When you unlock Beorn, you can transform to his bear form. just press and hold K.

Complete the Bonus Level
After you finish the story (all 16 levels) you will unlock the bonus level near erebor.

Complete the mining game perfectly 50 times
With Bufor you can mine gems and minerals. just do it perfect in the middle.

Equip Thorin with the Mithril Mushroom Crown
The Mithril Mushroom Crown schematic can be found a bit north of Bree.

Use Gandalf's startle ability to dazzle 50 enemies
You shold get this one on ''Azog the Defiler'' level. choose free play and get gandalf. you will be surrounded emenies, so just press and hold K to dazzle them 12-15 times.

Use 50 Buddy-Up attacks
In fact, you will get this achievement if in your way to the next one.

Use every Dwarf from Thorin's Company in a Buddy-Up attack
Make yourself a table and erase every combination you already did. Include Bilbo.

Equip yourself with Dazzle Wig, Mithril Rhythm Stick and Mithril Dance Boots.
So this one is pretty complicated because you need to craft the whole three items at the blacksmith:

• The Dazzle Wig is found in the "Flies and Spider Level", in "The Elves of Mirkwood" section.
  
• The Mithril Rhythm Stick Schematic can be found in the lake in Rivendell. You will need a boat to reach the area. Follow the studs to find the route that leads to the Schematic. Once to reach the pilars, you will need the Fire Cracker bow or Saruman to break the chest.
  
• The Dance Boots are also located in Rivendell. You will need to activate three switches to earn this Schematic. The first two switches are on top of the ropes that only elves can reach, and the final switch is at the very right of the cave. You will need to shoot arrows to make a swinghook

Obtain all Master Burglar titles. (Single Player Only)
You shold wait with this one until you get the multiplier red bricks. in some stages it's hard to get the master burglar without them.

Collect all Treasure Items in levels. (Single Player Only)
You should get the Treasure Item Detector red brick, before starting to search for the items. so that's what you have to do:
When you complete all High Fells missions, you will need to get Mithril Music kit to some goblin so he will give you the red brick.
to get the schemastic, go to the Lake-town, and look for a building you can enter near the center of town with a basement. There’s a cage and a hook point to the right.

Collect all Schematics. (Single Player Only)
You'll have the symbols of the schematics in your map, just be aware that some of them will reveal just after some quests.

Collect all Minikits. (Single Player Only)
You should get the Minikit Detector red brick, it will be a lot easier:
The schematic for the Mithril Bandit Gloves can be found in Lake-town. From the Lake-town statue, follow the stud trail to a door with an anchor on it, and go through.
After you craft it, from the "Thranduil's Kingdom" statue, follow the stud trail into the fortress and up the narrow path to a woman who will request a pair of Mithril Bandit Gloves.

Collect all Mithril Bricks. (Single Player Only)
Just make all the quests and get every mithril brick in your map

Forge all the Mithril Treasure Items. (Single Player Only)
You will unlock this one when you do the next one.

Forge all the Perfect Mithril Treasure Items. (Single Player Only)
When you find all Schematics you go to the blacksmith and there you can craft the all Mithril Treasure Items. you should make them perfect in the first time to save time later. for make them perfect you need to fill the inner circle.

Complete all the quests in Middle-earth. (Single Player Only)
Note that the red bricks quests are also counted.

Collect all characters. (Single Player Only)
It's pretty annoying but you need to get to the characters if you want to buy them. some characters a reveal after some missions, like Peter Jackson, the blacksmith of bree. you can get him just after you have all the red bricks.

Achieve 100% completion
if you get the rest of the achievements by now, you'll have this one too.

Collect 10,000,000,000 studs. (Single Player Only)
This one is the most annoying. you shold have the x2, x4, x6, x8, x10 multiplier and the Studs Attract red bricks. when you have them, you just have to get a lot of studs.
The best place on my opinion is Bree. if you ride on a warg you can travel fast in there and get a 150 millions studs in every time. after you clean bree, ride to the "Azog the Defiler" level and the studs in bree will be there again. Near Azog level, there are 3 trees with a purple stud between them. make there and back again to make a lot of studs as fast as possible.