The assessment starts on the threshold, not the holding point. Keep the briefing brief (aim for max 1 min), the details should have all been discussed in the briefing room with your partner beforehand (after they give you the plate). In the cockpit you should read the main points of the plate (RWY, SID, FREQs and verify your setup to the PM). Whilst you are setting up get the PM to request the weather, that way its ready for you after you setup (reference the wx at the start of the brief with a "weather is not limiting for a return") and the PM isnt twiddling their thumbs whilst you get yourself together.
After takeoff clearance state "straight ahead 3DME right turn heading 312 deg, call me 3 miles" and away you go. Sound confident and set a good tone for what's to come. You'll already have the assessor liking and believing in you by now (and thankful you haven't subjected him to a 5 min briefing bore fest).