I tried to show in this tutorial my way of drawing on RMD, but I also mentioned some general tips not used in this particular drawing. I wrote quite a lot -_-'. Hope it helps.
If you know exactly what you want to draw, set the most suiting background and draw a sketch on guide layer. Since guide layer doesn't use any ink and won't be seen in submitted drawing, you can try many things without worries. Since it's only a sketch, it doesn't have to be either smooth or detailed (look at mine, it's quite rough don't you think?). The lines and shapes you draw in guide layer are all in the same grey colour, quite visible on either white and black background. On the blue and orange gradient ones, however, it can be hardly visible, so be careful. Working with guide layer if you plan to have previously mentioned background might be easier, if you change to a white one when drawing on/comparing with the guide layer. Keep in mind that there's no way to 'erase' a part of sketch drawn on guide layer since there's only one colour you can use there. You can only clear all that's on guide layer when you save for later and then load saved drawing. Nothing that's on guide layer saves for later, so be careful not to load/exit until you're sure you don't need it anymore. It can be helpful sometimes, when the sketch becomes too 'crowded' and you can't determine what is what anymore. Save&load and it's clean again.
Here I'll describe one of my ways of colouring large parts quite accurately. First, draw an outline of the shape you want to fill colour in (in this method the colour has 100 at transparency meter). Look at guide layer to make it exactly where you want it. The thicker pen you use the easier it will be to use fill tool on it later, but the outline will be less sharp. I used a freehand one, because I'm used to it and I don't mind the lines to be a little rough. If you want them to be smoother draw an outline using many short straight lines. Remember to use undo button (or delete button on your keyboard) every time you don't like what you drew. Erasing things with other tools uses up ink and may not go well with your background if you chose a gradient one (mind that white and black ones also aren't pure, so if you really want to erase something it's better to pick the colour from the background with the eyedropper rather than simply selecting it from the colour palette).
Remember to check how your outline really looks by un-clicking the eye icon next to the guide layer making it invisible. Now's the time to correct any mistakes or smoothen the line. It'll be easier to do in a zoom mode.
Filling. Use the fill tool and draw on the outline you drew previously (if you prefer to fill with a pen, go ahead, I'm suggesting fill tool because it uses a bit less ink). Usually turning off the guide layer makes it easier, but since I didn't outline the ear I have it turned on here. And I didn't outline the ear because I wanted it to be sharp. It would be sharp if I used the thinnest pen to line it, but that would be meaningless while filling, I couldn't possibly perfectly fit the colour in such thin outline. Filling is easier with zoom, but that also means you can't fill really large parts of the picture. Just divide it to a few smaller and fill them separately. Since the colour isn't transparent at all it won't make a difference in the end.
Turn off the guide layer (if you have it on) and check for any holes between the filled area and the outline. Now's the best time to correct this, later it can be harder. You can skip some of the holes though if you plan to cover them later with some other colour, e.g. you want to draw a cloth or hair there.
When drawing a person it's convenient to draw skin first. Then shade it just after drawing the shape of it. An easy way of shading skin is using airbrush. Fill tool is also effective one, but harder to use (see my Lavi, Jasminum or Luger drawing to see how I do this. Or check Hanaoji2's drawings, in my opinion she's a master to that technique). Either way choose a noticeably darker colour than the base one and make it transparent enough to be hardly visible after a single use of a tool. Putting more and more colour on the same place but in smaller shape will create smooth shading. Before you start, decide from where the light comes so that there is consequence in your shading. Two or more light sources make it really difficult to shade properly. The same goes for not white light.
Airbrush tip: This tool uses up a lot more ink than any of the rest, ant it may make the picture look pixelated (don't worry on it too much, usually it will go back to normal when you submit the drawing. Sometimes it's visible during the animation, but it will stop when it finishes. The thumbnail could be affected by it though). Usually saving for later and then loading fixes it, but not always. If that happens and you still want to work on your drawing more, better undo the airbrush till the pixelation stops and try again, maybe with different method. Be careful not to overuse this tool, using it without thought won't make your drawing better and may ruin it. I think airbrush is good for drawing blurry background, shading skin, some fluffy things and for light reflections/shining effect. Using airbrush to fill shapes that should be sharp edged is a waste of ink.
Now for the hair. I decided to use a fill tool with low transparency to make them look delicate. Firstly draw a general shape of them, you can do it with a few smaller shapes, it's easier and more accurate. At first it won't cover other colours, but it will get more intense every time you draw on it again.
Just like that. Now I won't need a guide layer anymore, I can save it for later and finish some other time if I want (but I didn't).
I did the same with the hair in the back. Yes, it would look better if I drew them at the beginning, before I drew the face. If you can plan your drawing really well then I suggest you do so. I usually leave the background untouched until I finish the person because I'm often short of ink and I'd rather have a good drawn person with no background than a good background with not finished person...
Make the colour right, shade some parts of the hair, fill any holes remaining.
. I'm saving my drawing for later only if I'm satisfied with it or when I want to try something new-as a safety save (if you're experimenting, keep in mind that the guide layer will be cleared when you load!!). Just save anytime you think you should, you can always undo.
Last touches: shining on the hair and necessary outline. Lines put on skin will look softer if they're a darker version of the skin colour or similar (a purely black outline fits only in cartoon style or when all the lines and shading are sharp). You can also make them in a bit transparent colour, then there will be even less contrast. Lastly submit your drawing to website. :)