How to make my icon high quality?

When your drawing if able to change the DPI to at least 300(I normally do 600 but it is up to you the more DPI the slower your device may be). DPI basically effects Dots Per Inch which helps with resizing.

Save images as a PNG not a JPG or any other type of photo type. PNGs are better quality than JPG.

Don't work as large. I say if your just going to resize if a bust don't make the canvas larger than 1000 × 1000px as all your work just gets squashed. Though if your DPI is high enough the quality should still be good. I did my current icon, I work with a 500 x 500px canvases for icons and just resized to 150 x 150px and saved as Png.

I save images to Imgur as well as it has a hidden feature so that your images is not public but still sharable.

Hi! What kind of program do you use? Ive done some research into this because i wondered the same and this is what i found.

if you want a picture reduced without loosing quality, you need a certain program. You might be using a raster based program. It uses pixels. This is why it gets super grainy the smaller you go. And unfortunately its not really possible to get anything other than a pixel type tag with these programs. Other programs are vector based. They use paths instead, so they can reduce the image to any size you want without quality loss. If you want to shrink an image for a tag, you’d probably have to send the file to your computer with that kind of program and do it there. Or just draw it on that program. You can google which programs are raster based and which are vector based. 

I hope i explained this good enough. I’m not very good with programs and all that fancy stuff so don’t know if I make sense when trying to explain it haha! XD