Experienced network engineers, which advice would you give less experienced engineers?

Hi,

I'm 22. I've been interested in the networking for a long time (since a high school). I learn, repeat and try to avoid mistakes but still... I sometimes feel I could have done it better if...

I'd like to know which techniques should we avoid. Which techniques should we apply. Which sites / forums / channels should we regularly check but especially...

What could you've done in a different manner if you had had know-how.

I'd like to know general tips / tricks etc.

Thank you.