I have a couple of nasty looking moles and spots. Wondering what to look for to determine if I need to have them looked at, or whether not to worry.

Need expert. Innocent looking moles could be lethal if melanoma develops from it , let your doctors them if needed will refer to an expert . Some times need biopsy or removal for analysis ( biopsy )
NASTY LOOKING MOLES. I DO NOT KNOW WHAT YOU MEAN BY NASTY . . . I YOU ARE CONCERNED, DO SEE A DERMATOLOGIST.