butterbreaking instant crossholes from hallugenorific disorientation man dude I swear

[Davy Jones]

Well, you can see the whole tileset has two abrupt cuts. These cuts mark the borders for the three blocks. Then you just assemble each block separately, from the left to the right, next row, from the left to the right, etc.

A block can look like this:

Line 1
Line 2
Line 3
Line 4
...

Each line is a bunch of 16x16 tiles right next to each other. Line 1 fits on Line 2, Line 2 fits on Line 3, etc.
In short: Everything fits perfectly on each other and forms the tileset structures, no matter what it is (ground, tree, walls, etc.)

This is the theory. In reality, it looks like this:

Line 1 & Parts of Line 2
Rest of Line 2 & Parts of Line 3
Rest of Line 3 & Parts of Line 4
Rest of Line 4 & Parts of Line 5
...

TL, DR:
- You essentially need to know, for example, when Line 7 ends and Line 8 begins.
- Also you need a feeling when to leave or close a gap between tiles.
- Assembling is about left to the right, next row, etc.
- Lunar 1 & 2 have blocks within the tileset which have to be assembled separately, Astonishia Story & Legend of Mana don't have that
- Activate the grid in your graphics program or you're lost (Lunar 1 & Legend of Mana: 16x16 pixels, Lunar 2 & Astonishia Story: 8x8 pixels)

Edit:
Here is an example what I mean about the gaps between tiles:
http://i.imgur.com/9naSFfj.png
Look at the second tileset (with the furniture), you have to shift the tiles around to make them work. This opens/closes gaps within each line and is pretty much normal when you're assembling them.