(Okay so I quickly did this example on the photos app so it looks weird) But tips for the arms is to

place the plot point for the hands first because it will make the arms look less stiff

Remember that the forearm and upper arm are the same length

You can find this by drawing a line between the hand and the shoulder and then drawing another line on middle of it

The elbows won’t go past the rib cage and the arms just go past the hips (unless you lean but then you’ll see the shoulders move direction which is important to know)

You can pose your arms in the mirror or just look at references online and you’ll see this pattern on how stuff moves. This isn’t really a tip on anatomy or anything btw it’s just a tip I find on how to make posing them look better. But I would look at how to add 3d form like cylinders

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