When going digital, and going completely digital, You have to keep in mind that it can get really pricey. However, there are a lot of competing companies, and so different softwares have many perks, downfalls, and of course vary in prices. not to mention you need good equipment For digital art, otherwise you could lose hours worth of work to one error message!
Here are some useful tools to use when working with Digital Art:
    Hardware
        There are many kinds of programs to use, like Adobe Photoshop (~20 USD per month), Paint Tool SAI(~5400 JPY), Manga Studio(~210 USD), and Open Canvas (~60 USD), to list the pricier ones, Krita, GIMP, inkscape, MS Paint, Drawpile, and of course DeviantArt Muro, to list some free ones. There's also ones for things like iPad and other Apple devices, like Ibis Paint, SketchBook, Drawing desk, and many more. Most of these have free trials and/or free versions as well. Try out as many as you can! Remember, they're trying to be as appealing to you as possible, because that's what makes money, but at the same time, they want to be as different from everyone else as possible. Many people discourage use of certain apps and such because of the layout. Keep this in mind!! Getting used to a layout can be a big pain, but that's the fun part! If you've only used one kind of application, then you only know that one kind! Try using those free trials, along with looking at you-tube to watch people draw using those programs. Then you can actually get to know what you have to use!

    Here's some basics (more like stuff I've noticed):

   -- People tend to use Paint Tool SAI and Photoshop together. SAI is great on it's own, but lacks some effects. Photoshop has MANY effects, and people seem to use it AFTER drawing in SAI, mainly for effects and finishes, and it looks to be used more for digital pixel art.

    -- Also it seems like SAI has a new version, Paint Tool SAI2.

    -- Krita is like Photoshop, but with more/better brush choices, and free! (~PuNK-A-CaT).
    -- openCanvas has many different versions, version 1.1 being free, but pretty limited. If you get it from STEAM, you're also able to get the next version of oC for free (ex, you got version 5, then 6 comes out, well you can get version 6 for free!)

    -- SketchBook has both PC and iOS versions, and they have a group page on dA (autodesk-sketchbook). They also do monthly 'hero' challenges!

    -- WACOM, the (in)famous digital tool experts, have tablets that can connect to your PC to give you a second screen that can be used with some drawing programs like SAI. They also have pens that you can use with iOS devices! (I think they work best with iPad...)
    -- Be careful using ibis Paint. The quality can be anywhere from really good to really pixilated, which sucks. A lot.

Workspace
Here's a common-ish setup:

--monitor

--laptop/compter/second screen

--keyboard, usually wireless

--graphics tablet

--mouse mat, padded

--wireless mouse

    Keep in mind that your screens can make a HUGE difference. Something with a graphics card being shot or outdated can really hurt your works. I'm a good example. My art on my computer is actually pretty flat because when I go to use shades, a lot of the time my screen makes the colors look different. The top is darker than the bottom! I may think I have two different colors going, but when I go to pick up the other color, it's the same. It takes a long time to work like this and play around with colors.

Keep in mind your file sizes
File sizes are important

KEEP IN MIND YOUR FILE SIZES.
    Why? Because if it's too big, and you have a lot, you'll eat up your computer's memory. If it's too small, your picture will be, well, tiny. Which can be both good and bad. When you first go to 'open new file', the presets are something like 800x600 px. Meaning its 800 pixels high by 600 pixels wide. This is nice, but for a finished piece. While drawing, make it 2-3 bigger than you want, then go into Image Size, and bring it back down once you're finished. Your lines will be small, look nice and clean, and if it's for download, it'll be nice and small. There's also different kinds of files you can save it as. JPEG, PNG, and GIF are the common ones. If you're making a print, it's better to have the picture as large as your computer can handle. Okay not really but know what size you're printing the picture at, and manage that on the canvas. Usually you can change the size from pixels to inches/cm, or the program can sometimes show both. Remember to at least double it while working, and shrink when you're done. If you have to, save two images, one for the web and one for the print. Please note, I'm not talking about the prints you make for DA, I mean the ones people would buy at a con, but uploading large images on DA is possible so you can make more prints available. These files can become very large very fast, memory wise. Try to keep it under 2GB, if possible.

    Making a scan digital:
    If you want to draw the picture, and then scan it and digitalize it, usually the picture comes out gray-ish. You can use different techniques to fix this:
Clean it up: Adjust the image levels. This can make the darker areas become even more dark, helpful if you're only using pen. You can also mess with the Brightness and Contrast, though it can mess with the look of colors if you used color pencils. If you're not uploading it as a traditional piece, it doesn't matter too much. If you want to have both traditional and digital versions, remember to make a copy to work with for the digital. You can go through with a polygon lasso tool and select the areas you want to get rid of, you can hold the shift key down to make multiple selections, and then go through and either cut the sections or erase. this can be very time consuming, though. It's also a way to make the background transparent (make sure you go to View->transparent and make sure it's checked so you can see that it's transparent and that it saves transparent.
Or you can skip this step and just go over the lines (on a new layer!) with new lines. if you use a mouse, though, this can be hard and take just as long, if longer, to do.