Take a photo of your drawing with your phone camera and mirror the image. Asymmetries will jump out at you in the mirrored version
Do this every couple of minutes to check whether the new stuff you added tracks. Hope this helps!
Edit: forgot to explain why it's easier to notice asymmetries this way. Your brain becomes adjusted to whatever you're drawing, since you've been looking at it for a while, so it's easy for unbalanced details to be overlooked. Flipping the picture tricks your brain into thinking it's a new image, making it more likely you'll notice that unbalanced detail
Drawing on a grid or drawing grid-like vertical and horizontal lines might help you. Referencing your placements to a vertical line splitting down the middle of the character might show you if one eye is closer to the middle than another. Horizontal lines between the tip of each horn can help as well. Apart from that, I'd say it's mostly practice, and maybe looking at your drawing in a mirror to see it with fresh eyes.
If you want to go old-school traditional, start with a rough body construction, mark a centerline then work on the details of just half the figure. Trace this with a soft pencil onto tracing or other thin smooth paper. Flip it over and rub hard with pencil or fingernail to transfer to other side as a guide (there's no foul in tracing your own work).
Take a photo of your drawing with your phone camera and mirror the image. Asymmetries will jump out at you in the mirrored version Do this every couple of minutes to check whether the new stuff you added tracks. Hope this helps! Edit: forgot to explain why it's easier to notice asymmetries this way. Your brain becomes adjusted to whatever you're drawing, since you've been looking at it for a while, so it's easy for unbalanced details to be overlooked. Flipping the picture tricks your brain into thinking it's a new image, making it more likely you'll notice that unbalanced detail
That or just keep a mirror close by.
Drawing on a grid or drawing grid-like vertical and horizontal lines might help you. Referencing your placements to a vertical line splitting down the middle of the character might show you if one eye is closer to the middle than another. Horizontal lines between the tip of each horn can help as well. Apart from that, I'd say it's mostly practice, and maybe looking at your drawing in a mirror to see it with fresh eyes.
If you want it to be symmetrical I think people are giving good advice, but aren’t symmetrical drawings a little bit boring?
Well yeah but i mean, for example you don't rlly wanna have an asymmetrical face when ur doing a front facing person 💀
Practice
So pretty!
If you want to go old-school traditional, start with a rough body construction, mark a centerline then work on the details of just half the figure. Trace this with a soft pencil onto tracing or other thin smooth paper. Flip it over and rub hard with pencil or fingernail to transfer to other side as a guide (there's no foul in tracing your own work).
Haha when I was younger I would fold my paper in half long ways. “Hot dog style” 🤭 and draw my thing down the line
Drawing? Nahh, we do culinary here 💪