$A^\dagger$ - how to handwrite this?!

Lots of people use $A^*$ to represent the Conjugate Transpose.

To actually draw the dagger, draw a really long vertical line, dashed with a small horizontal. I personally dash the horizontal at an angle when I'm doing this so I know that it's a dagger.

I personally use the third style like I mentioned.

Never thought I'd give handwriting advice here, but I suppose this does fall under notation. I agree, the dagger can look like a plus sign. My rendition adds a guard to the dagger's pommel. Additional advantage: it's a single stroke.