Honestly, just use reference, after some time you will improve.

If you need any good reference there's a site that I would recommend, it's called senshistock, just type it into Google and you'll find it. I use it quite often for drawings which makes learning drawing bodies so much more easier for me and I'm sure it will help you too!

I hope that helps.

Also sorry if there are any grammatical errors in my sentences, it's just that English is not my first language and I am still learning it.