I firmly believe that no votes are wasted. Vote for the best person for the job. As long as we say that its not worth voting for that person because they'll never win, then they'll never win, will they.
We have Green politicians in government in Scotland. Irrespective of whether or not you think that's a good idea, voting for the person/party you want to win can have its effects.
There's another way votes are not wasted.
Parties receive "short money" which correlates with the number of votes cast. It's a major source of income for LibDems and Greens, neither of whom have the number of seats which represents the number of voters.