Make sure you set aside LOTS of time for the shoot if you plan to do it all at once. I do newborns and always tell parents to plan on spending 4 hours on the session. It doesn't always take that long, but when the time is needed, you will be glad that you've set it aside. If you are planning to pose the baby, do it slowly and in stages. Move one arm, stop, wait for baby to settle in, and then move the other, stop, wait, and so on.
Use side lighting if you're using natural light. I prefer to use a softbox with my newborns. I set up my posing bag perpendicular to the window (blinds drawn up). I put a standard umbrella light in front of the window (so I have the light from the window diffused by the umbrella, as well as the added light from the bulb, but I only turn it on when needed) and put my softbox on the other side, raised above the baby and aimed downward to light from both the side and the top. This also gives me plenty of light to work with for front shots. Lighting is key with newborns, as it is with everything, and I have achieved good results doing it this way.
I primarily use my 35mm f/1.8 lens for my newborns. My biggest mistake when I started was keeping my aperture too low. I always wanted to keep at that 1.8, 2 setting but I found that it was too low for certain shots, so adjust accordingly. Remember your depth of field and, if you are doing any side shots at all, adjust your aperture so that BOTH eyes are in focus, not just the one closest to you. It makes me crazy when I go back and look at my older newborn work and find only one eye in focus.
If you are going to use any hats as props, pose first and then put on the hat. It sounds simple, but it will save you a lot of heartache.
I then use post-processing to remove newborn redness and give that creamy, smooth newborn skin that you see in most newborn photography.