Aku: Some, hopefully, constructive critique is coming here =) I am usually to lazy to ciritique people, but i thought the linework on that picture was so good that i would like to help with a few pointers about the colouring and possibly line work =).
First, the lines. As I said, i think the lineart is awesome. The lines themselves though, could use some work. Sense your using photoshop i will assume your using a tablet. If not, then you can dissregard what i say here =)
I have no idea if you made the lines in photoshop, or if their the scanned lines from your original art. For a picture like this i would recomend to either scan it in a much higher resolution, or just redraw all the lines in photoshop to make them more crisp. Reason im saying this is because right now they feel a bit pixelated, and a cleaner/crisper lineart would go better with the choice of colouring you picked.
(If you want i could go in depth on how to ink in photoshop or illustrator). When inking in photoshop, its important to use pen pressure, so you can controll the thickness of the lines.
And speaking of colouring, I was in the same position as you last year and wanted to get better at colouring in photoshop. What you first need to do is to decide what kind of colouring you wanna make. I mean, sometimes one can see an awesome cell shaded pic, and think i wanna do that. And the day after that you see a more paint/water colour style and think thats the way to go. So decide what kind of colouring style you wanna do. An advice is to make one picture, and colour it in several ways and see what your most comfortable with.
The way you coloured this picture seems to be a mix of paint style and cell shading (with soft edges), and its nothing wrong with that, but i think it will be easier for you to focus on improving when you have only one style to focus on.
Random tips:
Avoid soft brushes and smudge tool as much as you can. A brush with opacity pressure sensitivity is much to be prefered over the other two. Soft brushes and smudge tools might seem cool at first, but you will learn alot more by not using them (they have their uses, but its better to learn how to shade without them in the beginning)
For the style you used to colour this picture, i would use more shades of the different colours, like the way you coloured her thighs. Thighs are very well shaded, the shirt could be better of =)
And thats it, hope i was to any help. And remember, only reason i wrote all this was because i was very impressed with the lineart =) Im also very tired, so i hope i didnt write to much nonsense.
And btw, heres the pic i made when i myself decided on how to colour:
Colour test by *RainyDaySunshine on deviantART
basically i just made a lineart and coloured it in different ways and then picked the style i thought looked best with the way i do my lineart (i picked the cell shading style, yea i know, its sort of lazy of me because it doesnt require as much effort. But I myself much prefer to focus on lineart, and i think colouring is a bit dull =) )
