Everyone's giving digital art tips, so I thought I'd dispense some traditional art hacks I used.
Not drawing techniques, but technical techniques.
Using the scanner is the best possible method for capturing your paper sketches, but what I found to be most presentable is taking a photograph of my work in sunlight. Place your canvas/sketchbook on a flat surface next to a window and take your picture. If you prefer full natural sunlight, it's fine, but avoid the afternoon. The exposure will fuck up your image and you'll have a hard time dealing with your shadow covering your work.
As for the camera itself, your regular phone cameras will do. Adjust the contrast of your shot if you have the option, it helps to expose your lines yo be thicker. After you take the picture, don't immediately swerve away. Stay still for 2-3 seconds for the image to sharpen after capture. This feature exists for most phone cameras after 2018.
If you're using soft, regular paper, be wary of how you erase your stuff. For example, I always erase my shit up and down. As a result, my paper gets creased sideways. If I take the picture, I'd see the shadows of the creases fucking up the image. I rectify this by just flipping the sketchbook over where the light shines parallel to the creases. Minimum shadows come out of that (but do try to minimize your erasing).
Make sure your camera's perpendicular to the sketchbook/canvas. It goes without saying that you don't want a fucked up angle while capture your item.
Filters are your best friends, don't be afraid to use them. Sometimes, cameras/lightning just don't make your work pop out. Using some contrasts/highlights/increased shadows will fix it. Though try to go moderate to avoid your shit looking like an overexposed piece from the 2000s. Just stay away from colour highlights and try to maintain the original hue of your work.
Speaking of filters, Saturation works absolute fucking WONDERS if you're using a colour pencil and got some white slits across your surface area (you know what I'm talking about here). As I said, try not to overdo it though.
If you're using regular soft paper, wait one night before taking your picture. Sometimes, a heavily adjusted sketch will creases the edges of your paper. Try to flatten the edges or, if you're running on time, tape the edges to a flat surface or something (I tape the back of the page to my sketchbook's cover), this will prevent some sneaky shadows piercing from the corner.
If you want to use Instagram as your choice of filters (like me), posting one photo at a time increases resolution. Posting multiple in the same post will fuck up the resolution from a crisp 5 MB to a 130+kB jpeg.
On the same discussion, avoid using the Structure filter on Insta for now. For some reason using it eats your RAM like crazy and will freeze your phone if you try.
Don't crop your work from your gallery. It will fuck up the resolution akin to posting multiple images at once on Insta. Try using third party cropping software. They'll sometimes even upscale the resolution from their in-app sharpening features.
Unrelated to trad art, ImgBB is a great place to store your portfolio, at least for me.
That's all I got. Have fun.