Is there one best way to save a scanned crossword puzle - as a .bmp file? .tif?
other?
I want to send it in a form that transmits easily and is then readable when the recipient opens it.
GIF.
There are really just two generally universal “standards” that you can be sure the receiving party will be able to view: GIF and JPEG.
JPEG is best for color, realistic images. GIF is best for computer artwork and low color images. Since your CP is presumably black and white, GIF is a win-win.
The only thing better would be to run OCR on it to make the clues and such into
actual text. Much more readable, but since OCR takes quite a bit of human postprocessing to clean up glitches, not a lot of fun to do. But then you have the problem with what format to use. There is no comparable standard for mixed graphics and text files.