When you first spawn in on Earth, if you look to your right there is that square building with a load of Dregs and Vandals outside it. If you go underground from there, you see a room that is empty with a chest room in it, normally 2 yellow bar acolytes and 1 yellow bar knight will spawn in there.
This trick to get these spawning again is that you can run outside the room to the left a bit and run back, by the time you have got back in they will have spawned again but if you here the sound of a skiff coming in, you will need to kill those fallen which are located right next to a patrol mission beacon on the right. After this you can you back down to the spawn and the majors should be there waiting for you. I will make a YouTube video on it if people don't know where I am talking about.
Edit 1: This is mainly for Christmas noobs so don't be hatin' and stuff just because most of you will already know of it.
Edit 2: DON'T TURN RIGHT AND WALK OFF A CLIFF.
Edit 3: You can go both ways, left or right.
They -blam!-ed with the timer on these guys. I used to firm them all the time. I'd run down there kill them, run out of the hole in the wall and turn and come back and they'd already spawned. Now it takes forever.
I just usually now go with the first moon mission. Killing everything but the Knight,letting it kill you, restart the checkpoint and so on.
You can also do the mission where you destroy the crystal on the moon. That has 10+ hive majors on it.