general Prolog hints 
  when defining predicates
    don't use hyphens in identifier names
    indefinite iteration can be implemented as recursion
      but avoid left recursion
  when in the interpreter
    don't reload in the middle of a trace
    dealing with error messages
      note that line numbers and column numbers are given 
      don't worry about "can't redefine ,/2"
        this is just a syntax error, usually an obvious one
      many errors result from replacing a comma by a period, etc.
      if you get an undefined variable error message 
        don't worry about "If these are defined
        at runtime using assert/1, use :- dynamic Name/Arity."
    dealing with warnings 
      do worry about warnings re singleton variables
        can use an anonymous variable if you really want a singleton
      you probably do not have to worry about the warning re
        clauses of a particular predicate not being stored together
    if there's a typo and you can't back up, 
      try typing a period to end your query
      you may need an end quote, right brace, etc.
    if you don't get a prompt when you expect one (e g., after error)
      you may have left a definition, string, etc. uncompleted.
      if not, try typing
        a space, or ^C, or a (for abort)
      or just go ahead and type your text
  there is a Prolog text in the library coures reserves
  don't forget about the manual available in the Help menu