Get the Dressing Room:
To receive the Dressing Room, finish all areas and quests under normal difficulty.

Unlock hard difficulty:
Finish either episode under normal difficulty to receive hard difficulty for both episodes. If you get to level 20 or higher to receive hard difficulty in online mode.

Unlock very hard difficulty:
Finish either episode under hard difficulty to receive the very hard difficulty for both episodes.

Ultimate difficulty:
Finish either episode under very hard difficulty to receive the ultimate difficulty for both episodes.

Avoid walking near traps and enemies:
Normally, you cannot run when near a trap or enemy. To avoid this, push Start to view the main menu. You may now run again.

How to beat Dubchics:
Notice that they return to life. After killing a Dubchic, a brown orb with yellow rings around it should fall to the ground somewhere in that area. Annihilate it and all the Dubchics will be destroyed.

Get cheap kills:
If you are having trouble in a room, try running out of it and go back in. Some monsters will probably go into a dormant mode and allow you to get off a hit or two before they retaliate. This is especially useful against Garanz.
 

Refill your health:
If you are a robot in the game, you can refill your health after receiving damage from an enemy. Find a safe place to rest and remain in that spot for a least a minute. Your health meter will go up a little bit at a time.
 

How to fight invisible enemies:
Use the environment to help you. Enemies such as Sinow Zoa can easily be spotted by their reflections on glass or water, as well as the targeting system. However, that can be unreliable at times.
 

Resta Dodge:
With the correct timing using the technique Resta, you can miss almost any attack. The trick is to just cast Resta before your enemy attacks, but long enough that you can gain life; otherwise you will just get hit.
 

Easy level gain:
If you want to get some levels without much effort and are around a 25 to 40 level range, try going the forest levels under hard difficulty. You can usually get about 8,000 experience points from it.