I've recently acquired an 8-channel relay from China. I've been reading and watching a lot about how to connect them to the RPi. For now I've only tried it out on an old RPi Model B (I didn't want to fry my new Pi), and it seemed to work great.
However, from what I've been gathering online, the best practice is to connect the relay to external power, so it doesn't draw too much from the RPi, but also so I can use the 5 V and 3.3 V for different purposes. My question is now, how would I go about doing this, and is it in fact the best practice?
The relay I've purchased looks like this:
and I've bought it from this page, which contains some (quite limited) documentation of the product:
I hope some of you accomplished makers can help me with this problem.