I think it's important to greet magpies ("Good morning Mr. Magpie" - adjusted for gender and number). That isn't superstition, it's science. Not sure how one greets a dead magpie, though - "Rest your soul, Mr Magpie", might be worth a try.
Number thirteen is a problem for me. I NEVER go fishing on the 13th of the month - by choice I won't go anywhere other than to honour essential commitments such as work. It's not that I'm concerned about blanking - hell, no; I'm doubtful that I'll get there and back intact!
Again, it's nothing to do with superstition; it's science.