4 – 6 months
Lay your child in their bed on their side. Ensure they can’t roll onto their stomach by placing your hand on their chest. Lean over the crib (this can be a little back-breaking, sorry) and firmly pat your child’s back, patting between the shoulder blades. You need to shush, a long drawn out shhhhhhhhh, past your child’s ear, not right into it. This isn’t always the easiest thing to do, don’t injure yourself, and don’t shush too loudly directly into your child’s ears.
Give them a few minutes. If your child doesn’t settle, pick them up and hold them to your shoulder. You can continue to pat and shush. When your baby has relaxed and their breathing evens out, lay them back in the crib, continuing to pat and shush.
If your child stays quiet, start to slow the patting to a stop, but continue to shush for around five more minutes. If your child remains calm, slow, and stop the shushing. It can take up to 20 minutes for your child to fall asleep, so don’t rush off. Your child is in a deeper sleep when their body relaxes, and their breathing slows.
Make sure you gently roll your child onto their back before you leave.

6 months +

Lay your child down in the crib. Try to leave, though chances are your child will get upset, roll over, sit up, or even stand.
Begin by soothing them with your voice. If that doesn’t work, you can pick them up to soothe them. Hold your child horizontally, and don’t let them fall asleep on you.
When they stop crying, immediately lay back down. Lay them on their side and place your hand on their chest so they don’t roll onto their front. Reassure and talk calmly. Rub your child’s back, pat gently between the shoulder blades, or maintain gentle pressure.
When your child seems to have settled, gradually withdraw your hand and back slowly away. You can talk soothingly to let your child know you are still there.
Your child may realize you have moved away and may begin to fuss. If your child rolls around, sits up, or stands, wait until you need to help them before returning to the crib and restarting the process. I know it can be tempting to rush and help your child as soon as they begin to move. Children may sometimes check what’s going on and then settle themselves, so don’t be too quick to come back and intervene.
If you are making a move to lay your child down and she begins to cry before you have even got her into the crib, continue to lay her down. You can pick her up straight away if you need to

As your child becomes comfortable with this technique, they will fall asleep within 10 – 20 minutes.