The gang is giving lots of good advice. I'm new to tractors, myself, and will pass on three things that I have (almost) learned the hard way:
1) Focus on the task at hand and be situationally aware. This means know who and what are near you (360 degrees, all around, above & beneath) at all times. It's amazing how quickly a dog, a little brother, tree limb or a 'chuck hole can appear "out of nowhere" right on top of you. Don't get distracted ... "oh, look, there goes another red tail ... that's the third one I've seen this afternoon" ... you get the idea. Don't let people distract you.
2) Pay attention to your loading/ballast situation. It is usually changing depending on what you are doing. Turn hard left and your center of gravity (CG) moves left. Lift a bucket full of rocks and your CG moves up. Try to keep your CG as low as you can as much as you can.
3) If you start getting frustrated, impatient, annoyed, turn the key - shut 'er down and just walk away. Come back only when you are calm and able to make good decisions.
Have fun - I love the feeling of inertia that only heavy equipment gives you.
-Jim