I have a Pi powered with its own adapter. I bought a 1 meter ws2812 led strip and bought a separate power supply for it (5V 6A). I plan to plug the +5V of the power supply directly to the +5V section of the led strip and the GND to the GND led strip and to the GND in the raspberry pi (pin 6). The DIN of the led strip will then be connected to pi's pin 12 (GPIO18/PCM_CLK). Am I doing it correctly? Is it safe to have a common ground for the led strip and the raspberry pi? Is it okay to have separate power supplies? Do I need to buy voltage regulators and or level shifters?
Reference: http://frederickvandenbosch.be/?p=1014