I'm not sure if I should be adding this tip since it isn't my own but one I found online.
(See the link above. I hope it continues to be OK since Burda is ever-changing.)
I've always been frustrated when trying to get a nice, defined point on collars. I found this tip on the Bruda website and used it on a denim jacket I'm making. The fabric is SO thick and somewhat stiff. I thought this thread-assist technique worked very well.
After the collar is turned you can leave the thread in for the next step of topstitching. I gives you a "handle" to pull on when you turn the corner so that little collar tip doesn't get eaten up by your sewing machine.