The main advice I seem to see is "stick in a group" or "snipe from the back"

If you stick as a group, you are very easy to flank. Also, two arcbolt grenades will kill your entire team.

The key for our tactic is area control. Split up, and go to different areas of the map. But do not rush at them. Push them to where you want them (know what firefights you can win). Attacking from different angles is important here.

If you're sniping from the back, you will get rushed, and from different angles if the team is good. If you're good with a sniper, this will work for you. If not (like me) you probably won't win the firefight.

Also, just because somebody keeps killing you with thorn, doesn't mean you're going to be good with thorn. There's a learning curve with all weapons in the crucible, so use what you're confident with.

If you're primarily a PvE player, don't come to ToO expecting to go 9-0 with ease. You will have a huge disadvantage to crucible veterans, especially those who play a lot of skirmish.

If you get 9-0 on all characters, go to crucible lfg and help out some players who are struggling. Its quite a lot of fun.

Also, if you're winning a team 4-0 go for a NLB round. Its fun, if you win, its a win well deserved. Doesn't matter if you lose a round or two, and it will give the losing team some hope!

Most importantly, have fun out there.