SolZen here again with another Help Page to teach you how to draw a transformer. Now note, this page expects you to have some level of experience drawing.
This is info I put together from looking all over the internet and I hope it helps.
Part 1 Edit
The first step to drawing a transformer is simple, draw a skeleton. No, not an actual skeleton, a series of lines and circles that represent where the body and limbs will be and the position they will be in. Remember to draw a chest area and a line to show the pelvic area/hips.
Part 2 Edit
Now here is where you design you robot/transformer, you could just start by drawing a basic robot, but then you add elements of their alternate mode. They are a transformer, even if they are in the Movie style, their robot form should show characteristics of their alternate form. This gets trickier when you have a bot with more than one form.
The alternative is to just draw the basic shape and then add elements of the alternate form. Regardless by this stage you are determining how your bot transforms via the choice of elements you put on and where.
Part 3 Edit
You should design the head first or separate from the body before you draw it on. It helps to make things look better.
I would advise drawing the basic shape of the head before adding, the side/cheek armor, then the helmet and the helmet's crest/decorations.
Part 4 Edit
You could have done this in part two or three, but you should have designed weapons, you could have just drawn them in or design them separate and put them in. By this stage you should also be putting in the final touches.
Alternate Form Edit
So people would saw you determine this first, others, after, personally I don't care. Regardless to draw an alternate form one should...know how to draw a vehicle.