@Sherrieh
Likeness is one of the hardest things to really nail down.
However I think you will benefit most from simply improving your line and your construction of objects in 3D space.
My advice is to practice drawing continuous straight lines. That's all! No going over a line twice, no chicken scratching. Long, continuous lines. They'll be wobbly and that's okay. Once you have done that a little, draw boxes. Fill them in with hatching.
Basic drawing exercises are boring as hell, I know, but they're really good.
Here is a demonstration, clarification picture and some more.
http://imgur.com/a/ZaOt7
In the first picture, 1 is a chicken scratchy line I drew. Not good. You can have a scratchy style, something like Hajime Ueda's style, but even that has tight line fundamentals behind it!
2 are smooth lines. They're less precise, but that's okay. I can get them tighter: but even very high level pro artists have kind of shaky lines if drawn from the elbow or shoulder. Smoothness and confidence first.
3 is a smooth curly line, 4 is a chicken scratchy one. After that another smooth one. Do these yourself and you will see a difference.
5 is just varying pressure in the line. This is fantastic practice, do it. It doesn't have to be any particular shape if you're going for pressure practice. Just vary the pressure and get used to the tools.
6 are hatched boxes. Pay attention to how I draw them. It's one line and smooth. It's okay if the lines go a bit over each other or aren't 100% straight.
In terms of grip, the 2nd picture in the gallery is how people usually hold a pencil or pen. This is how most people write.
I suggest holding it in the way as I hold it in the 3rd picture. Instead of using the index and thumb to tightly grip it, rest it between your index and middle finger and higher up on the shaft.
It's looser and much less precise at first, but after some months your line quality will increase tenfold and you will decrease chance of wrist injury. Draw in a more loose style if you're afraid of mistakes.
This was very difficult for me to learn specifically because I have somewhat shaky hands AND I death grip everything which causes more shakiness. I am much more relaxed nowadays in my drawings and have more precision, but when I started, it was impossible and I kept going back to a tight grip when I needed to do tight lines. Just trust your brain and it will sort itself out.
Hope it helps and you find more reasons to draw! The best thing for me would be to see people improve at art here and post more of theirs.
Here's my share of WIP for today. Apology in advance for the potato picture: I always draw at late hours during holidays or weekends.
It's gonna become a trend that I don't finish stuff because I always find something new to work on from them. I'm also much more of a technical artist or a designer, so working with figures is a big weakness of mine. In every picture I make I find more than ten things I can improve.
I finished watching Shakunetsu no Takkyuu Musume lately. It was dumb as hell, but somewhat entertaining. Then I realized that there's really not that much table tennis themed art in a manga style. So I got to work.
I did a generic sketch first, the one on the left. There's a lot of bad lines and erased bad lines, but that's part of the process. I figured out some things I need to work on, namely drawing table tennis rackets from various angles and having them be accurate.
I tried a TON of poses, but I wanted to go with a generic Japanese peace-sign because I'd do the Japanese team first because it just seems appropriate.
The anatomy is quite difficult for this one actually (We don't usually see the arms and chest from this exact angle), so I'm gonna need to take a look at some good reference later if I want anything that looks half decent. I'm drawing this mostly from the head so it's a bit more challenging. Canvas is also WAYYYY too small to make the hands look any good. Use a decently big canvas if you're doing "real" work.
I then did a very quick study of Kasumi Ishikawa. Realistic faces drawn with the bare minimum of lines, with no shading and no stylization look creepy as hell, but you'd be surprised just how strange real faces look this way. Better artists produce better lines so it's not as creepy.
Once I kind of have an idea of what the main features of someone's face are, I stylize it a bit and add some shading if I'm gonna be doing a sketchy picture, so it doesn't have an uncanny valley effect and the lines are more beautiful. Maybe later I will do one of these, but it's kind of not necessary because I have the picture in my mind already. I might just for the practice.
A good example of very realistic faces without enough texture and form to support them is Aku no Hana. Google "Aku no Hana anime" and you'll see what I mean. Aku no Hana was indeed rotoscoped (Drawn over pictures of real people) on purpose to make it have a strong uncanny valley effect for storytelling purposes. It's more technically accurate but god damn is it creepy. A big part of art is "suggesting" something, not really trying to show it exactly as it is. If you take away some essential things about how reality looks and exaggerate others, it ends up just plain wrong.
The last on the right is a sketch of a Stiga Clipper with some Hurricane on it. I'm gonna do probably at least 40 - 50 more studies so I'm really not concerned with how it looks: these are throwaways and you shouldn't feel bad about having throwaway pictures!
This is more or less how I think about some art related things. I'd be interested to see/read OP's process. A lot of artists don't post early WIPs or ugly crap even though all good artists do a lot of ugly crap, so it kind of distorts things. If your WIPs and work process is beautiful, then it's even more credit for you, ahahah.
I think some time ago a very good artist posted here once with a WIP. What happened to them? I can't remember exactly who they were or where they posted.