I believe that the crate/kennel is the way to go if you are not able to be with your puppy all day long. My boyfriend and I work, so we put Hercules in the kennel during the day. We also put him in there at night.
Start slow by introducing him to the kennel and making him feel comfortable. Some suggestions are to give him a treat to go in there, feed him in their, put his favorite toy in there. Once he's in, close the door and keep him in there for 15-30 minutes, while you are still around. Slowly increase the time, and even leave for a little bit. Make sure he knows that the kennel is a good, fun place to be. They should like their kennel. Never put him in there as punishment.
Those are my pieces of advice and the things that we did with Hercules. He's a little over 4 months, and we've had him for 2 months. He still whines a little bit when he's first put in his kennel. But it quickly stops and he usually curls up and goes to sleep. Oh, and make sure the kennel is really comfortable - blanket, pillow, toy, etc should be in there for him.
Keep us posted as to how Hero is doing and be sure to show us some pics of your new baby!!
Brandi & Hercules