Here would be my advice; and I am somewhat new myself!
1. if you get a loop tangle (that is, the thread you are working developes a loop that you can't shift easily), put your needle inside the loop and gently but firmly pull on the thread outside the loop until the loop shrinks. Then pull on both ends to make it vanish. unless something has really happened to make it tangle, this will generally work. Patience, haste makes waste, and similar sayings apply!
2. Keep the brain engaged. Don't zone out... that's how you make mistakes and invite in the
(that means have to rip stitches out that are wrong.) Constantly cross-check what you are doing, sanity check that it makes sense and if you detect something amiss, stop until you either figure out what it is or convince yourself that all is well.
3. When you select a design, make sure you really like it. You will be spending a lot of time with it... don't settle.
I'm sure there is more but I hope this helps someone!