Periodically, I have people ask me about how to get started in digital painting. I decided to write up something to use in the future as a response to that particular enquiry, since it's far from a simple answer. You could call it my lazy reply. To be fair, it's a pretty loaded question, and it seems a lot of the people who ask don't realize how much they're actually asking. I'm not a teacher or personal tutor, mind you, so this will have to do.
First of all, one of the most important things for you to know is that digital painting is not some magical solution to making awesome art if you can't already do so with regular drawing materials. I don't know why I have to say this, but it seems like a lot of new people have this idea. The basic skills you require to produce a digital painting are the same skills you'd use to produce a traditional drawing of the same quality. The software does not do the work for you. If you're aspiring to paint, whether digitally or traditionally, you need to work on basic drawing skills first if you want any kind of results worth looking at. You can have the most expensive software and high-end hardware in the world, but if you can't draw, your paintings will look like shit. Learn to draw.
If you have no idea how to draw, I would suggest this book. (ignore the left brain/right brain fluff and take in everything else)
If you draw already, the above book might still help, as well as all of these.
It is important to practice drawing a lot. Whatever it is that you're interested in, draw it- repeatedly. Draw it from different angles, in different positions, etc. until you have a thorough understanding of it. I would say to also draw things you're not interested in, but I think that all depends on your goals. If you're wanting to, for example, get a job in the game industry as a concept artist, you'll have to be able to draw anything and everything. However, if you're just wanting to paint for your own enjoyment, then by all means, just focus on what you like. Practicing drawing anything at all will enhance your drawing ability overall, to a certain extent.
Make sure to use references. Even once you get really good, you'll still need to make use of references. Anybody who tells you that referencing is a crutch or a sign of a bad artist is either full of shit or incredibly naive. It's important that you know how to use them correctly, though. Now, it's always recommended that you use a live reference whenever you can instead of a photo, but I'll be honest, I never noticed much of a difference. I have various defects in my vision and my depth perception in particular is poor, so I always assumed this was why. Taking that into account, I will assume that you have normal eyesight and give the same recommendation of live references when possible, and add that if you're going to use photos, use lots of different ones from various angles. That's usually what I do. Here are also a couple of really well-written tutorials on using reference photos:
I know it seems like a lot of work, and it is. I've been doing this for thirteen years. Go and look at my progress meme if you haven't already seen it, and you'll see how I started out. I don't mean to sound like I'm trying to discourage anyone from pursuing art- far from it. It's just that I get frustrated when the odd uninformed person comes to me wanting "a tutorial" that teaches everything there is to know about digital painting. Drawing and painting are very complex and time-consuming pursuits- if you want to get good at it, that is.
Now, all that said, getting started with digital painting in particular is mostly a matter of experimentation and getting thoroughly acquainted with your software. Click around, experiment, see what everything does. When just starting out, I've found that looking through tutorials is helpful. Browse tutorials here on DA and even follow them if you like, to see how others do things and get an idea of what works for you. Youtube has loads of helpful digital painting videos, too. There's no one right way of doing things, and the technique you end up using will depend on the effect/style you want to achieve and what you are most comfortable with.
If you're wondering if you have to have a graphics tablet to paint digitally, the answer is no, but it will make your work a LOT easier and faster. Holding a pen is simply more natural and easier to control than a mouse, and the pressure sensitivity is a huge advantage. I have seen some really stunning paintings done with only a mouse, so those who can't afford a tablet, take heart- it can be done. But if you're tossing up between getting a tablet or not, just get one; it will be worth every penny. For just starting out, Wacom's Bamboo series is good- they're modestly priced and good for just about any kind of work. Once you know you're in it for the long haul and are willing to spend a bit more money, the Intuos series is well worth it (I use an Intuos 3). There are other brands of tablets out there that I'm sure are perfectly fine, but you'll have to do the research on those; my experience is mainly with Wacom.
It all basically boils down to practice, study, and experimentation. There are tons of resources out there for getting started in digital painting, if you only search for it, and I'm not going to do that for you. This is the internet, you've got a virtually endless supply of knowledge at your fingertips. If I can find out whether or not cats can smile, or how to start a fire with a condom, you can find some information on digital painting for beginners.
And just because I'm feeling generous, here are some good digital painting tutorials for you to have a look at. Keep in mind that you can still learn something from a tutorial even if it's not made for the software you're using; most programs have a lot of basic functions in common. These cover different skill levels and styles of painting, so take whatever helps you and leave the rest. A few of these might be a little more advanced, so you can always skip them and come back to them later if you like. Feel free to look through my favorites, too, as there are a lot more neat things in there.
Hopefully, all this has been helpful to you somehow. Again, I'm not a teacher, I've just had several people ask me about this, and while digital painting isn't brain surgery, it's still not something you could sufficiently explain in a journal or tutorial.
And before I forget, for those who want to know, my work is almost 100% digital. On rare occasions I will sketch on paper and scan it in, but I mostly sketch directly on the computer. I use Paint Tool SAI for most of my work and Photoshop CS4 for a smaller portion. I use a Wacom Intuos 3 graphics tablet and do all of my work on a desktop PC. I've never gone to art school or taken any classes; everything I know, I've learned through independent practice and study.
If you have any questions, go ahead and ask me in the comments and I'll answer you as best I can.
Good luck to you, and I hope this was worth something. 
Somebody give me a gold star.
Somebody give me a gold star.
and then stopped practicing my drawing on paper for some insanely stupid reason hahaha and then learnt how wrong I was! So I am now working on the whole learning and building up process (slowly haha) so this is so perfect 
so thank you very much for your perfect/helpful/inspirational post 