Carrots don't yield much juice but it tastes great and if you mix one carrot with half an apple and juice them most kids will drink it and enjoy it
Beetroot are pretty strong; personally I love the flavour but it can be a bit 'earthy' for some people. One small beetroot packs quite a punch. You have to cut beetroot up fairly small as it is very dense.
Celery is also fairly strong, but is incredibly health (so is beetroot!) so it is worth it!
Too much spinach in one go clogs up my juicer
Too much parsley can have a laxative effect.
Lime, lemon and orange juice all contain vitamin C which will help prevent oxidation which helps preserve the benefits of juice if you are not drinking it immediately.
For extra greens you can juice dandelion leaves, sorrel leaves, even nasturtium leaves...(haven't tried nasturtium yet though!)
Kids love feeding veg into a juicer!
The next post will be on the health benefits of different juices...