* Keep this thing pristine. Dust, corrosion, liquid, or any other indignity will invisibly poison the breadboard and take its toll on your sanity later.
* Use only DIP legs and 22-24 gauge wire. Shoving a TO220 into these spring clips will spread them and take its toll on your sanity later.
* Decouple, decouple, decouple. The distributed inductance of a breadboard is nontrivial and if you're not putting a nanofarad next to every logic chip, you will summon ghosts.
* Buying cheap breadboards with subpar contact plating will yield exactly the sort of performance you'd imagine. Breadboards are supposed to be an EASY way to build circuits, not a CHEAP way. You get what you pay for.
With all these things in mind, they're quite good at what they do.
(digital circuits are fast analogue ones!)
The whole video series is excellent. Highly recommended.