anyone know the trick or any hints to getting them besides just luck?

Go in as a team. Simple.

anyone up for some invasion then?? lol

well i got the kill 5 spartans as an elite achievement and also the wingman achievement as well. i just have the skunked one to get and then all i need to do is the weekly and daily achievements and then the ranking achievements and then it's s-rank for me(atleast until the new achievements drop. lol)

Skunked is probably going to be more luck than anything else - you have to hope you get matched with a group of people willing and able to work as a team.  I've only played a handful of Invasion matches, but I'd say the majority of those only lasted one round, so it shouldn't be too hard to get.

i'll prolly just get some friends together and do it. i almost had it a couple times but then the rest of my teammates left me and the first round defense places alone and all got picked off and left me to defend the positions a minute before the time was to expire so yea =/

Just play the game, thats how i got them.

This achievement is much easier to get on Boneyard than Spire. In fact, the first phase of Boneyard Invasion is more difficult for the attacking team to complete than any other phase on either map I'd say. The best way would be to gather a team who knows to stay on their side and defend but also help out when the objective is being captured. You definitely want to have people who know how to use the DMRs pick them up and pick off people approaching. You also want to check around the entrances of the base and make sure no Elites are just sitting there letting there team spawn in and get easy rushes inside. If you spread out the team properly at the chokepoint entrances of the base and have people shooting into the spawn as Elites are coming in it shouldn't be too hard to win.

Play with me.