On paediatrician advice we started DD at bang on 4 months. Honestly, it was really a waste of time until nearly 6 months. She barely ate a thing and it was just frustrating. I think if they're not ready they just won't eat it! She is still mega fussy and only eats a little bit of fruit purée and rice cereal.
Next time I am not going to bother until I see clear signs of readiness rather than just basing it on age.