Can't tell it for 6502... but for Z80. Because was my first own "computer":

* a single Z80 (which was nicer than 8080, because the latter needed an extra clock IC) * 256 bytes of static RAM * 1 8bit D-Latch (Flipflop) with 8 LEDs * 1 8bit D-Latch with 8 dip switches * 2 8bit buffers that can go tristrate between the hex-thingies and the address & data bus * 2 rotating hex thingies: you could rotate them between 0-f for data * 2 rotating hex ones for address

Now, how did it work? I pulled nBUSRQ down (bus request). This made the Z80 go tri-state. It also made my buffers non-tristate.

Then I used 2 of the hex-thingies to set the address and 2 of them to set the data. Now I set nWR to low and that would write the entered data byte into the SRAM.

When I was done, I turned nBUSRQ back to high, so the Z80 again was the boss of the bus. And then I simply used nRESET to low to make the Z80 execute my program starting at address 0.

I did only tiny programs, like adder, some PWN/sound wave program, an traffic light simulator.

But, since I soldered this all by myself, I had no "monitor program" like the KIM-1 had. So I had to do all of that by hardware.