1. Odds or Evens
In this type of clue the answer is hidden in either the odd or even letters in a word or phrase. The indicator is generally 'Odd', 'Oddly', 'Even', 'Regularly' or something to that effect.
2. And Lit.
In this kind of clue (generally indicated by an exclamation mark) the whole clue is both the definition and the wordplay.
You will very occasionally see clues that don't fit into any of our categories. They are often entertaining and do not have to follow any particular rules. One good example of a clue that defies classification is the infamous:
which clues WATER.