- 1)The Jaws
Males generally have almost squared jaws, even those who have narrow faces have a squared jawline. Also, the chin is never pointed, it's either squared, clefted, or rounded (As in the example) And the lower jawline is defined in the male physique, it dosen't smoothly curve into the socket like in most bishie drawings. (Note, the noticable jawline is something that naturally exists in both males and females, but in a lot of artistic renditions, the defined jaw is usually a masculine feature) Also, before I forget, males have muscular necks (usually, sort of like in my example) and, in some cases, Adam's Apples While the definition of these two aren't needed, it does add a bit more realism to your guys.
2)The Eyes
You know those pretty eyes a lot of bishounen are drawn with? Yeah, you can just forget about those here. In manga styles, the eyes are a defining feature, since they show the characters emotions. However, a manly looking guy with large eyes looks creepy, so we're going to shrink them. In my examples, these are just a few ways I do my eyes, but there are many others. The thing to keep in mind is to keep them from being too big (This is where a bit of realism comes in) At their largest, the eyes should reach just where the bridge of the nose begins. (This is also something you can take back and apply into older females as well.)
3)The Arms and Body Overview
When a male is going through puberty, their muscles become more defined. Even the scrawniest of males has some sort of muscle on their arms (unless they're malnourished,in which case bony arms are acceptable) they also develop muscles on their abdomens and legs during puberty (Again, unless they are either malnourished or underweight). Though, something that I've noticed in most bishie drawings, you can't be scrawny AND have noticeable muscles. It can only be one or the other. (This is because muscle can make the abdomen much larger since it is denser and larger than fat)
4) Facial and Body Hair
The bane of all Otome lovers: male body hair. The moment the guy enters puberty, he begins a lifelong battle to control the growth of hair on his body and face. Ladies and gentlemen, facial hair CAN be attractive (It is defininately in real life) and can be a lazyman's way of showing a character's age and experience just like a guy's clothes and posture (Ex. A guy with a soul patch, dressed in a unbuttoned dress shirt and cargo shorts probably gives you the image of a laid-back kind of guy.) So don't be afraid to add a bit of fuzz to your guys, since us males naturally grow it whether we like it or not! And as for body hair: most guys grow a noticeable amout of hair on their arms, legs, and chests(Also known as the Carpet of Virility) Dosen't mean it's impossible to find guys who grow no hair in these places, but it's rare (Unless they wax frequently, or got some expensive treatment)
I'm not saying that this is the only way to draw masculine males, but it is ONE way. Take what you want to learn and use it.
EDIT
Never writing another tutorial before I go to bed. Here's a handy proportion chart: