I do compare sized of one limb with the size of another as you suggest... But i rarely do them helping lines along with it though, i draw stuff out of the blue...
To exlpain this further, i really have to ellaborate on how i made this torso sketch here to begin with, the progress of it may- (uhh, or may not, i don't know many artists and their ways to draw, to be honest haha) -appear kinda untraditional;
I've drawn out my lines with color, each indicating which came first, and when something was added around it... (yellow needs to be highlighted i see, haha)
Notice that no helping lines such as bubbles or squares to indicate the position and size of stuff are there, i used none such, but started drawing details right away
1) Red was my first line, it was the breast2) Green was my second line, the other breast3) Blue was my third lines, down the belly area, and adding plating on the breasts and such4) The brownish red, the shoulder pads were the fourth details i made, to kinda find the shoulders location... Note, that i didn't use help lins there, i actually guessed where they'd look 'right'... Afterwards thugh, i added shoulder through the shoulder pads as seen, but those were actually a final touch to the whole sketch, and not something i added before or right after the pads5) The yellow was the neck and colar... It was also here i overlooked the sketch to see if it seemed anatomically right, after which i refined the lines everywhere to make it prettier and stuffReference image is here below
So, rather than making a set of bubbles or squares and all that to determine how what looks before detailed parts are added, i add tehm right away, and reefine them at the end...i also like to draw each set if limbs out completely, like one fully detailed arm with fingers and all, and when it looks right, i make the other arm, instead of making two undetailed sketches of the arms to figure if they look right that way...
I really dislike using references... I feel i'm by cheating using anything beyond my memory of how things should look, although i KNOW professional artists use references as well... But it still feels not right when the memory is perfectly capable of knowing how things should look...
It's partly also because it saves time to just draw them out right away, assuming i DO get it right the moment i draw it (-since if i make a mistake, i end up erasing and changing more than i wanted to)... It takes longer to make out a complete sketch and then add things to it... It's faster making them right away, but not as safe, but it helps unpatient people like me getting done in the wanted amount of time though...
I ended up writing awfully much here, i hope it's not too confusing ...
Anyhow, don't take this on a means of me defending myself (it would be awfully arrogant if i didn't take well against constructive critism, rude too)
I am explaining what direction i took when i made the sketch though, so assuming it's not too confusing to see what i explained, it should be easier to tell how to improve on that... Since, i believe i don't follow the traditional way of doing things, so getting suggestions based on traditional ways wouldn't really do me any good, unless i changed of course... But as i explained, the traditional ways take more time and i hate using much time on stuff...
-It's still not too confusing is it..?