I know this may seems overly complicated, but it's really just a more methodical way of saying: "I find out the X, Y and Z of a point in the picture (which may seem really complicated but really isn't once you get the hang of it) and try translating it to my drawing's space"

So, basically, I was am doing that whole insect drawing thing and noticed that I was having trouble drawing the creatures' little legs because they are often rotated at some really (how can I put it?) organic angles.

Problem was, whenever I tried to eyeball them following my intuition, as much as tried to remind myself of the fact that each leg was actually distancing itself a bit from each other at all axis at once, they always felt flat, as though they were parallel to the insect's side plane.

Basically, I was aiming for a cricket's leg, that distances itself from the thorax in this organic, diagonal way but ended up with something more akin to a crank lever.

My solution was to use a technique I learnt from isometric pixel art. I took a reference picture and tried to roughly figure out what direction its X, Y and Z axis would point to, then I would use this information to figure out the coordinates of each joint relative to the previous one, which basically boils down to figuring out the lengths of the X, Y and Z that add up to it's position. (note that I am not actually keeping numerical track of anything, I am thinking of things in terms of lines that exist in 3D space).

With the coordinates in mind, I would then translate them to the X, Y and Z of my drawing (which would be different because the insect wouldn't be drawn from the same viewpoint), which required the aid of some landmark such as the head of the insect.

With the Drawing's coordinates figure out, I would then imagine it as three lines placed on each other's tips, hovering over them with my pen until I arrived at its end, where I would place the point.