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At youtube you can type "draw pixel art" and some good ones will show up, and they give nice tips to start, like this by Goodgis, but don't limit yourself by 100% what the tutorials say, listen to the tips, and pick those that better suit or make sense to you. I learn by doing a lot of mockups for personal projects that I never released 😅. Some tips I can give is,  with a small canvas (128x128 or 256x256) start to make small sprites (8x8 to 16x16, but you are free to choose any size) and make random things and different versions from it, this helps you to train your style. Try to draw daily too, make a challenge to draw at least a different object per day, a box, a chest, a sword, a tree, etc. Don't fear to challenge yourself too, try new things sometimes, like animations, tilesets, big drawings, etc. Look for reference at old games, how they did it, look at Twitter the #PixelArt or #ドット絵 and follow the ones that inspire you. With time you'll start to get better. I'm at this journey to improving too, always there's something new to learn.