The main things I've learned are:

1.  Greens are greens, for the most part.  You can substitute for whatever is cheap and easy or whatever your personal taste preference is.  Use kale, spinach, any lettuce, cabbage, chard, bok choy, turnip greens, beet greens, etc.

2.  Peel your citrus, except for lemons.  And always leave as much of the white pith as possible...there is good stuff in there.

3.  Core your apples.  You definitely don't want those seeds in your juice.

4.  I love juicing because nothing goes to waste.  If you see things you have starting to wither, use them that day.  If you're making broccoli for the family, throw the stems in your juice.  The ends of vegetables you might normally throw away?  Use them in your juice.  The peels you usually throw away?  In your juice.

5.  You can throw all of your fruit and vegetables in the sink with a little apple cider vinegar and sea salt, let them soak for 10 minutes, drain the (now filthy) water, rinse them like crazy and voila!  They're perfect.

6.  Using spinach?  Rinse it again.  Dirt sure does get hidden in those leaves.

7.  Doing a juice fast for weight loss and not eating any food?  Take a b-12 supplement of you'll crave meat like crazy.

8.  Drink a lot of water.  And have some with you all the time.

9.  There are things allowed on a juice fast that you can't really juice, like bananas and avocados and coconut.  You can make whatever juice you want and then throw it in the blender with those things.  I loved bananas blended in with orange/pineapple juice for an occasional treat.

10.  Your kids will drink what is offered if you keep offering it.  Much as my taste adjusted to only juice, they started saying the juice tasted sweet to them after only about a week.

11.  You'll need something hard to push the soft stuff through.  Carrots can be your best friends, even if the recipe doesn't call for them.

12.  I rarely strained my juice.  That little bit of pulp  can be really delicious.

13.  Blackberries juice great...but their seeds will juice right through.  Strain it or you'll be sucking seeds. :)

14.  That's all I can think of for now...