Lash Mapping directions:
Step 1: Tape your lashes. Note the base of the very inner and outer corner lashes, this is where you will begin. 
Step 2: Mark your inner corner and outer corner. To correctly do this, mark your lines where the natural lashes start and finish(figure 2). Not where the eye starts and finishes (yellow) or where the gel pad covers(figure 3). 
Step 3: Determine the desired style and mark a line where the longest lashes will be placed. I give two examples below.
In the first example, the longest lashes are in the center of the two orange lines (starting and ending points), meaning the longest lashes will be placed in the center for an open-eye look.
In the second example, the lingest lashes are closer to the outer corner of the eye for a natural sweep look. 
Step 4: Finally, let's fill in the rest of our map according to the directions and desired lash maps.
In the first example below we have determined that the longest length (12) will be in the center and the shortest length (9) is in the inner and outer corners. Given that we will use lengths 9-12, I will fill in the rest of the diagram for a smooth transition 9-10-11-12-11-10-9. Refer to the first example below for a visual.
In the second example we have determined that the longest length (12) will be closer to the outer corner for a natural sweep. Since we know the shortest length we will use is a 9 and the inner corners are usually shorter than the outer corners, I will label the inner corner with 9 and evenly divide the space between 9 & 12 with four equal spaces so that I have 9-10-11-12 from the inner corner to the longest-point and will use my judgment for the lengths on the other side of my 12. In this case, I will only use 11 for the outer corners. The final lash map for example number two is 11-12-11-10-9. 
Please refer to General Lash Maps blog for 12 classic lash maps you can follow.