W_1:You can learn something from my mistakes

1.LED's anode and cathode:

I only found after more than 10 failures that I inserted LED with wrong direction.
A(anode) and K(cathode) !!!. Longer leg is A and shorter one is,,,

2. Right use of resistor:
I thought that I can use any resistor from the kit, but each pack is different. Be careful. Yet there is no clear sign on it. Is there?

3. Check current flow with a tester more often than you think enough
You can find out on which point current is not flowing with a testor. Try it. It's fun.