Component side: Check for stand-up resistor leads touching one another.
Check for backwards caps.
Check that all 100ohms aren’t supposed to be 100k, and vice-versa, and 470/470k.
Look for stripped wires that could bend over and short something out.
Put all ICs in their sockets
1uF, 10uF, 100uF, diodes, LEDs, 2N5089, 2N3904, 2N5485, and all ICs must be in the right way. Replace any component that was backwards when power was applied.
If an IC connection looks suspicious, check for continuity between the solder side and the actual IC pin on the component side