there are a few 'signs' that labour is on its way, however on its way could be hours for some people, and weeks later for others!
The only true signs are regular painful contractions.
However some people have a show as their cervix softens, nesting (caused by an increased in prolactin, interesting enough suppressing this can stall labour, strange but true!)
Some people have a bog poo as your baby clears a path, increased cervical discharge, backache, a dragging feeling... the list is long and very subjective!
People always ask things like that! It's like when they ask if you have a 'good baby'!
remember induction is your choice, you don't have to accept.
natural alternatives include caulophyllum (I swear by that!), sex, orgasm, nipple stimulation (all 3 produce oxytocin, which has been linked with onset of labour), clary sage and finally just relaxing and let your baby decide when its time to come!
Good luck!!