Seek out mentors, make connections and keep them. These are often more valuable than technical skills. Of course, making such connections and acquiring mentors is a lot easier if you're effective at what you do or distinguish yourself in some way, so skills and accomplishments are also very important.

Seek out experts in the fields you're interested and start a correspondence with them and meet them if possible. Ask their advice about things that interest you and that they are experts in.

Many times in your life you will be faced with a choice between the hard road and the easy road. Most people take the easy road to mediocrity. You can further distinguish yourself, learn a lot more, gain more skills, and grow tougher by choosing the hard road.

Learn something thoroughly. If you are an expert at something you will be in demand. Generalists and jacks-of-all-trades get a nice, broad perspective and can make connections between fields that narrow specialists can't, but usually it's more feasible for specialists to broaden their horizons than for a generalist to become a real expert, especially later in life.

Be persistent. If you can master the skill of doing that which will improve your life and the lives of others no matter how unpleasant or boring that task is, especially over the long haul, then you will accomplish much more than most, who tend to easily give up and move on to something else.

Related to this, whenever you start something that will take a long time to finish, expect that there will be boring, frustrating periods where everything will seem hopeless. Plan well ahead of time what you'll do to overcome them when you'll encounter them. This is a place where your mentors and experts in the field can help, as you can ask them for advice when you run in to a roadblock.

Surround yourself with people who bring you up, not try to drag you down to their level or who are completely unmotivated. Always try to be around people who are smarter than you, who are better than you at something you're interested in, and who you can learn from and be inspired by.

Don't study for the test, but value knowledge for its own sake, to learn useful skills, and to improve yourself. This connects to the next crucial point:

Read A LOT. You can gain many lifetimes of experience through books. Real books, not blog post and tweets. It would not hurt to start by reading through "the classics", but often lists of classics overlook much excellent foreign literature, so try to seek out the best of what different cultures have to offer.

Travel (when the plague is over). Few things can open your mind to what is possible, let you meet fantastically interesting people, have unforgettable experiences, learn about other cultures and ways of being, and open up new opportunities for you than travel.

On the subject of travel, I would advise you to go off the beaten path and avoid super touristy areas. Stay in hostels.. it's a fantastic way to meet people and can save you a ton of money too. Don't try to see too much at once, and try to stay in one place for a good week or two, if you can, instead of doing 7 countries in a weekend.

Once you've traveled a while and got a taste of many different countries you're bound to find a favorite. Try living there for a year or two. You'll get a perspective on the place that a quick visit will not give you, and let you use it as a base for exploring other places in the area, and you'll gain even more valuable connections there that you couldn't as a mere tourist.

Learn some foreign languages. This is yet another way to make great connections and get to appreciate other places and cultures at a level you couldn't if you were just monolingual. It'll also open you up to the literature of other countries on a level you just can't get by reading it in translation. Many books don't even have translations, so you'll be at an advantage there too.

Learn to like yourself, enjoy your own company, and be your own best friend. Always seek out new subjects to learn and new teachers to learn from. A great teacher can make anything interesting.

Exercise and take thorough stock of what you're eating to make sure you don't have any nutritional imbalances. This can greatly affect your mood and energy levels, and ultimately let you live a lot longer and with many fewer debilitating conditions than you'd have otherwise. A sure way to physical misery is to not take care of your body.

Finally, try to help people and be as useful to them as possible. Apart from this being the right thing to do, it's also a lot more fulfilling than being purely selfish, and people are usually glad to be of help to someone who's helped them. So by helping others you'll be helping yourself.