Its not always easy. And sometimes can be annoying....SG teaming can be great or just plain out stupid....My thoughts...
Okey, so SG teaming isn't always trustful..Like sometimes they can just betray you just for the stuff you got. Or sometimes they're actually nice to you, and have trust. But sometimes, you get those ppl that are just like *I'm gonna gain some1's trust by teaming them then kill them* So thats why I really never team, even tho I love SG.
Dem Annoying Ppl
Those ppl who are just like "Can you team with me? Team? Team plz? Team with me and I'll give you stuff..I'll meet you over there!" Omg its just annoying sometimes. I just try to ignore those ppl who say that cuz its super annoying....Sadly you can't do /ignore in SG so you can't ignore them *At least I don't think :P*
Most ppl don't want to team with me becuz my skin doesn't look "professional" So...make your skin "ugly" or "nooby" *Or even just Stevie xD* to try to make them stop....
Hackers
So sometimes the can just be a hacker...and theres an easy way to determine that. If your just playing normal SG, with the most common plugin. If they have diamond stuff, you can know right away their hacking xD But some servers are exceptional becuz they have different plugins WITH diamonds...So be careful around that xD

But also ppl can just betray you...I've had expierences like that too. Okey so first off: I was on a server, and this guy was like "Team Jill?" Im like SURE WHY NOT, WHAT COULD POSSIBLY GO WRONG...and I got iron and stuffz and they killed me :c
Second off: I was walking with my teammate, searching for ppl and chests; I fell in a hole that I couldn't jump out of *I DON'T EVEN KNOW WHY SOME MAPS HAVE THESE....* and they looked at me and they killed me becuz I was trapped ;c

So yeh :L Don't trust evry1...Unless its like your bff from MC teaming is fine XD Otherwise, only trust some1 if THEY TRUST YOU *wait nvm you cant tell if they trust you lol* But still...be careful... O.o