Before any other progress can be possible, the baby needs to be comfortable with lying on his/her belly. Thus, you need a comfortable piece of carpet or a blanket where you can talk to or play with your baby while he/she is lying on the tummy. Make sure you maintain the face-to-face position with your baby since this will make him/her happy and comfortable and allow both of you adequate conditions for communication. So, you can place the baby on a sofa and lie next to it.
The Crawling Program
Once your baby is accustomed to the above mentioned position, make a roller from a towel, or buy any other type of a soft roller, except the inflatable ones. Then, take the baby's elbows and place them close to his/her body, as if he/she is supposed to rest on them. During all this time, if necessary, provide support. Afterwards, place the roller underneath the tummy of the baby, supporting it, while at the same time allowing the baby to distribute his/her weight onto his/her elbows.
If you managed to do all this, here comes the most demanding part. Namely, you are supposed to stand in front of your baby, facing him/her and start calling, amusing or encouraging him/her. Alternatively, you can use a mirror in front of the baby to achieve the same effect.
Therefore, the whole point of this exercise is to motivate your child to start using elbows and legs for support, while resting the belly onto the roller, getting used to the position. When you have practiced this enough times, you will be amazed by your child crawling with no problems.
Five minutes daily may be enough for satisfactory results in the long run. To recapitulate, the point is motivating the child to observe and explore the world around while resting on his/her belly, even while lying down this way.
If, perhaps, your baby cannot move from the position on all fours, you can lean over and press the bottom of his/her feet, for encouragement and support. Finally, making a special track for your child to move on and placing it on a slight incline will surely be a great motivation for him/her to move in the right direction, using the crawling skills he/she has learned.