Like most things in electronics, fields overlap so learning one thing may end up with learning 5 things, take this as a warning that this is the tip of the iceberg.
After you learn ohms law most people then forget his friend power (Wattage):
- try and size your trace widths to suit the power across them (Every Trace is a resistor)
- try and size components to keep them reasonably cool where possible, or if not possible try and keep things that are effected by heat away from that area, (E.g. electrolytic capacitors)
- If you have high impedance signals, a thermal gradient can offset your voltages (Think thermocouples)
Try and visualize where each current loop is, if your device outputs 1 amp, 1 amp has to return to it to complete the loop, be it through a ground trace, or an unintended route.
Even if you have a slow signal, e.g. a user pushing a button, you can still be dealing with high MHz edge rates, as such, proper decoupling, input filtering, and such should be looked at.
With I/O where possible try and protect it, for analog/digital inputs this generally just involves a current limiting resistor, for outputs, say a transistor switch, a base resistor can act as a crude current limiter, for some other outputs, there is not much that can be done to help,
I have typed up much on this on this forum, here is one such instance just about ground planes...
https://www.eevblog.com/forum/beginners/ground-plane-tell-me-more-about-it/Or if you want to be able to understand what is happening in a high speed circuit and traces, this is about the best thread on such a beast
https://www.eevblog.com/forum/beginners/how-do-they-%27know%27/