If I can believe all the Patrick O'Brian I've read then it is bad luck to have a parson/minister/priest aboard. 'Wimmin' as long as they are doing manly jobs are alright and rats are just the food you want when the provisions get low. It is bad to have a nubile unattached woman aboard as it can and will distract the crew.
Fridays are definitely out for leaving on any sail so why are most races on Weds., Sat. and Sundays?
Too many landlubbers aboard and not enough able bodied crew is another bad indicator.
Not superstition but if the shore birds start heading towards land then the weather might be changing for the worst. Watch the sky and be alert as if you were driving your car on a highway.
Wind does not always travel in a straight
line.