There are many different types of juicers out there and I won't go through them all but the one I own and recommend if you don't have a whole lot of time to spend juicing a day is the Breville Elite or Breville Ikon.
They juice quickly and efficiently. You don't get as much juice from leafy greens as compared to a masticating juicer (like an Omega) but they are faster and clean up a whole lot easier. One tip I can give is to run the pulp through the juicer a second time and you'll get about an extra 1/3 of a cup.
My go-to green juice recipe
1 head of romaine
1 cucumber (peeled if not organic)
4-5 leaves of kale
1 thumb sized piece of fresh ginger root
1 lemon
2 organic apples
Put a few ice cubes into the collection cup (chilling this juice makes it even tastier).
Juice on low setting: romaine, cucumber, kale and ginger. Juice on high setting: lemon and apples. Enjoy!!
My kids and I adore this emerald jewel of a juice and they demand it everyday. Yum!