The problem with giving advice to a group of children is that for some it will be irrelevant because:

1) ... they follow it already
2) ... they never take advice from adults
3) ... it is over their heads

EVEN SO, if the advice changes for the better the life of only ONE listener in a group then that is "a result" as Tom Barnaby would say.

Advice may also of course come under the heading of "the bleedin' obvious", but as far as that is concerned, I learned a nice expression years after leaving school which impressed me a lot:

• "Cela va sans dire, mais cela va d'autant mieux en le disant." (Talleyrand)
• "That goes without saying, but it is even better if you DO say it."

There are many bits of advice one might give to a youngster, but one of my favourites is this. Find some moral and/or interesting and if possible useful skill that you REALLY enjoy - and practise it until you are VERY GOOD AT IT: doing card tricks, guitar-playing, doing different accents and impressions, juggling, chess, painting, telling jokes and so on. Another idea is to become an expert on a few great historical figures or periods: Celtic Britain, the Norman invasion, Da Vinci, Faraday, Newton, JFK, Alexander the Great, Descartes - WHOEVER or WHATEVER  INTERESTS you. At the right moment you will be able to do your party trick and/or play a full part in the discussion - AND impress people!

The skill you acquire will be a lifelong asset. Even if you don't earn your living at it it will give great pleasure AND impress people. It is only a bad thing to try to impress people if you do it to excess so that it becomes boasting. But it is a pleasure to see someone performing some skill that is interesting - a party trick if you like. Who wants to be at a party without a party trick or two? You will give people pleasure by entertaining them AND make friends. That is not the ONLY way to make friends, but it is a good way.

People are also impressed by someone who has shown the dedication to master a skill or field of knowledge.

At a basic practical level, you may be asked at a job interview one day about your interests. If you say "the Renaissance" (your favourite historical period), then you really need to be prepared for follow-up questions as the interviewer seeks to determine how serious you are.

NOBODY at WHS ever told me this directly, but the staff DID make an effort to enable us to try out as many different activities as possible: the unstated aim being to encourage us to follow our interests and deepen our knowledge of them. That is most obvious in the number of actors and musicians WHS turned out - but there were other areas of interest, too. THIS is a list of the clubs and societies that WHS boys could participate in.

http://www.whs-archives.net/docs/janus/clubs.htm

One other really nice skill is to learn a few quotations you can slip into a conversation. Proverbs are fine, but almost everyone knows the usual ones. Quotations are a different matter. My WHS teachers didn't really push this point. We learned quotes from Shakespeare of course - and some lines of the most famous poets, but I think we missed out otherwise. In hindsight, we could have had a "Quotation of the week" from someone famous to discuss.

I love quotations, and have made a collection here: http://www.vervinomni.net/id/phil/def.htm

These are great minds speaking to us from the past.