3. Keep them contained somehow: You don't need to hold them tight, but put them in a safe place like a basket, or on a swing or between pillows.
4. Outside photo? Shoot in the magic hours: If you plan to shoot outside, you will get an excellent result if you shoot within what Pro photographer called: THE MAGIC HOURS, which is 1 hour after sunrise OR 2 hours before sunset. Again, natural light is your best friend!
5. If it doesn't work today, try again tomorrow! Newborn babies are unpredictable like many other things in life, many things can be wrong at the shooting time, don't push your little one. They may feel sleepy or there might be a teething going on. Be patient and reschedule for tomorrow when you'll more chance to get that lovely smile.