Ooh, kudos for the thread title!
It might be better to learn anatomy and overall observe the way you draw and improve your skill before having a take on as complex thing as realistic-in-a-way humans...
Hum, Oh well, I guess everything you draw teaches you something. So let's observe a bit:
- The positions of the eyes and the mouth are a tad odd, and also change between the different pictures. There're some really good examples out there that easily show you the relations between the parts of the face & head.
- It's good imo that you didn't do those generic huge-eyes, but instead kept the eyes in a reasonable size. The eyebrows are also rather good. I'd suggest you try checking some different examples of the outlook of an eye, perhaps study a real eye or just check some different online "how to draw manga eyes"-tutorials. It's quite important that you don't get stuck with a single eye outlook, but instead combine different ones and decide which fit different persons best. The current eye design is quite blocky, and along with the minimalistic nose they leave the face a bit flat.
- The character looks also overall a bit flat, mostly due to the fact that you've portrayed him from the front, with a very basic pose. Also the blockiness and sharp edges of the hand/overall give a inhuman feeling. You could try to draw different perspectives and poses to learn the basics of how to make things look natural; even if they didn't look exactly right, trying different and harder poses is a very good way to learn anatomy and relations of the body parts (, which currently are quite off).
- It's great that you've tried different angles for the head, too - it's often a sign of a less talented artist to portray the characters straight from the front or straight from the side. The proportions of the head are quite off, especially around the ear - also the position of neck compared to the rest is a bit too low, and the forehead of the character is pretty much nonexistent. Don't worry about these things though, there are several ways to learn them and at first it'd be best to just draw.
- It's great that you've added some different-looking clothes and accessories to the guy; even though later on an artist can show the distinction between characters just by their faces, in the beginning giving different kinds of accessories is a good way to separate characters.
And yet one more thing to come: one of the things most shown other than the faces of the characters are their hands. Many people attempt to hide the hands behind the backs of the characters/out of panels/into the pockets (not implying you'd be doing this, it's just one picture), but really, you'll end up drawing thousands and thousands of hands in different positions and poses, holding some swords or waving to people. It's really not as hard as it looks/sounds to learn the proportions of a hand, but once you've learned it, it's a really helpful thing! Also legs are the same, but not in the same extent as hands.
Overall, it's great that you enjoy drawing and try, but you just need a tad more practicing before handling the thing fully (oh well, no one can handle it fully - so let's say "handle it better"). Even though my comment may sound ranty and over-criticalistic, in my opinion it's no use to say to everything "looks cool" because that doesn't tell the creator where he should improve and what is good. Especially when it's about manga, that is often thought as "easy way to victory" but is actually a pretty tough path. I'm sorry if my comment upsets you, but I suck at writing other than criticism.