Standing up, Gently shake your knees, while safely holding the baby. If kneeling make a gentle bobbing up and down motion as though in water with a gentle wave current. You can go side to side as well.
If baby has gas s/he won't sleep, rub back while placing at an angle so that any resultant sick will come up unrestricted. You can do this with the above exercise. Allow baby to burp, can take hours so avoid anything fizzy!
finally, baby might pick up any stresses, whether in family, or on caregivers face. Always keep calm, try to look pleasant with a nice smile, a mild smile will do. One that says 'I'm pleased to see you'.