6. From Diognetus: to avoid empty enthusiasms; to disbelieve all that is talked by miracle-mongers and quacks about incantations, exorcism of demons, and the like; not to hold quail-fights or be excited by such sports; to tolerate plain speaking; to have an affinity for philosophy, and to attend the lectures first of Baccheius, then of Tandasis and Marcianus; to write essays from a young age; to love the camp-bed, the hide blanket, and all else involved in the Greek training.
empty enthusiasm - i take this to mean "all talk, no walk" if you are genuinely going to do something, then do it. do not talk about it. don't talk of being enthusiastic about something; rather, demonstrate it! (see this tweet)
there are many who want to convince you of their power; and they will do so by "miracles" and "exorcisms" and "incantations" just know these are fruitless.
quail-fights - i can't be sure, but i suppose this could be similar to cock-fighting. this is all wasted time and money. this does nothing to improve the person. as for entertainment value - it's all sugar and no nutrition.
tolerate plain speaking - to me, it means to let people speak bluntly (un-politically correct). to be sure, we should speak with respect and intelligence. but we should also allow others to speak plainly.
philosophy and essays - philosophy is none other than finding a good way to live this life. and i can think of no better philosophy than what the stoics endorse. reading and writing about philosophy helps us to think about what it all means and how to live it.
the camp-bed / Greek training - good advice. learn to be uncomfortable. learn to tolerate camping, hot and cold weather, sleeping on the ground, cold showers.