The key is that you are a crew in the sim. You are unlikely to pass while your buddy fails - you tend to pass or fail together, so act as a crew. It is pointless being the best single pilot operator of the 747 sim BA have ever seen if you let your sim buddy do something stupid and say nothing - it merely proves you are not a team player. It is far better to be told to stop helping in the sim than be deemed to not not be a team player.
Be yourself, there are plenty of places available so the only person you are "competing with" in the sim is yourself. Be a team player, it makes everyone safer and that is what BA wants. Handling is important but NOTECH skills will get you through the assessment.
BA loves TDODAR and plane, path people. It also likes you to operate at the Think Ahead end of the SA spectrum. all this is easier if you think and act like a member of a crew.