My friends simply dangle the baby's favourite toy and try to lead their baby to turn over. Try to dangle it such that baby will slowly learn to shift his/her weight to one side and soon, he/she would be able to flip over.
put some colourful soft toy in front of her.. Tis will help them to push herself forward and it will help her to crawl..
I will put toys in front of them and motivate them to move upwards (a form of motivated them to craw too)
I put some rattles or bells.