One habit I did learn in high school is writing x as two 'c' shapes in a mirror image. This is clearly an x rather than a multiplication symbol. I prefer it to the version listed in the article.
I find it hard to distinguish the author's X/χ
What's your subject?
I started crossing z's and doing a few of the other tips (some taught, some natural) in this page when it became necessary. But the pedantic in me really wanted to instill it in my kids from the get-go. I suppose experience (going through the problems of mixing up symbols) is the best teacher for the mathematical handwriting solution.
(And in both cross product and curl, if you substitute a \cdot, then that's an entirely different operation!)
This is an unbelievably ugly handwriting quirk which is sadly prevalent in some European countries.
If you do this the ghosts of dead calligraphers will come puke on your paper.
(Also, the cross product is always a less elegant alternative to the exterior product, but I guess this isn't the place for that rant.)
No, often you will use nothing - simple juxtaposition.