It is easier to build strong children than to repair broken men.
i taught mine to question everything and assume nothing!
i taught them others deserve as much respect as you do, and that no one is any better than anyone else.
simple, and it seems to have worked...
Don't teach them what to think, teach them how to think.
I have been going through this with my daughter lately. She is 7 and I have just withdrawn her from RE classes at school because they are going to be taught by a vicar who will present Christianity as true. I told the school we are not Christian but in the UK they have to have 15 minutes communal Christian worship a day and RE has to be Christian. I did not exercise my right to exclude her from these because she would miss all the school plays and house points etc. I have withdrawn her now after they told her that God turned rivers into blood and killed all the first born children - in a good way, of course.
Anyway, what I find works really well is to give her little lessons on all sorts of religions and present none of them as fact and give her lessons on evolution which is fact. By showing her how many religions there are and how many strange things they believe she is coming to the conclusion that none of them are right. I am pleased about this. I present them respectfully but say 'The Christians believe this while the Hindus believe that.' and the message she is getting is variety and choice - no fact. She likes the Christmas story and also the concepts of Karma and reincarnation but does not believe anything implicitly. We tell some stories from each culture which she likes but she does not see Christ as any more likely to be real than Thor and Odin and sees them all as stories. I think this is positive - I'm not vetoing religion and making it interesting or telling her not to believe but the result of all this information is lack of belief.
I teach my children to think on their own and arm them with knowledge based on facts and tangible evidence.