A question I get asked so many times during talks at camera clubs is
How do you decide when to convert to Black and White?
Sometimes the answer is easy (in a general way) - Covert to Black and white when
The image is inherently black and white
When the image contains lots of concrete
When you want to add drama/nostalgia/age to an image
Dont convert to Black and White when
Sunrise
Sunset
When the image is dependent on colours opposite one another on the colour wheel
When colour is the key aspect of the subject (ie tomatoes)
Here are some ideas from other photographers