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Tips for Junior Programmers
What is the best advice you can give a novice/inexperinced programmer, witch would help him the most in the long run of his carrier?
The best advice i've ever recieved was "Make it work, before seriously optimizing it". (Later I found out that he's was inspired by the famours line "Make it work, make it right, make it fast").
The tip is good to solving tasks most efficiently.
Become at least vaguely proficient in lots of languages/paradigms. That way you're likely to know what the best tool is for a given job.
"Do it because you love it."
I think programming can be a mugs game and you really need to love the work. If you don't then the drive to make it "right" and to learn etc just isn't really there.
If you want this as a career then you really need to love it and dedicate yourself to it. It's long hours of sometimes unrewarding work. It can be heart breaking to ditch code you'd worked on for sometimes days and it's hard to take criticism from others.
I know this isn't strickly what you wanted as an answer but I see a lot of programmers that don't love it who stay as mediocre programmers or who are unhappy.
Before coding anything, grab a pencil and design the solution/software/program/system, (even for tiny pieces of software).
When in doubt, make it a Console application. If you've reached the stage where you've identified a need, but not a user interface, create a "Console App" project that reads and writes to stdin & stdout.
In a sandbox world like computers, you have the freedom to make solutions rather PERFECT. It is tempting for many people to go hyper-perfectionist with code, but this is an instinct which all devs must learn to regulate in the pursuit of productivity.
Learn from others as much as possible. You will make many mistakes along the way, but why make the mistakes others have if you can learn from them?
on the other hand, mistakes and errors are what makes you grow as a programmer and as a problem solver, don't get frustrated because you can't solve a problem. treat it as a challenge and find ways to fix it or go around it.
If you are stuck on a problem and can't seem to find a solution, move on to another part of the project and forget about it. I promise you the solution will make come to you when you are least thinking about it.
REST!!! don't spend 3 hours in front of the screen stuck in one issue. Get up, take a walk, take a nap, drink water, and don't let it fester your head. Again, the solution will come when you least expect it.
Good luck!