Hi Kamla
Lateral thinking is as good, powerful and effective as Positive Thinking. What I have practised, these tips can be helpful
1. Thinking about the possible outcomes, even if the first response that the mind generates is 'nothing can happen', or 'only this would have to be done', or 'that's the only way, I am not left with any choices'. Just ignore that and send a message to your that I have to think it over and come up with atleast five or more alternative solutions. And see you amazing inner giant awakening.
2. You can start practising some meditation or concentration exercises, this also enhances your lateral thinking. I myself am a meditation trainer and I have seen wonders happening in lives of people.
3. I had this presentation from net some time back on Lateral Hats, hope you will enjoy this as well.
Do update me with your valuable feedback as this guides for further improvements.
All the best
Neeru Agarwal