GD round next week — how do you get your first point in without cutting someone off?

Our placement drive has a GD round next week and my biggest worry isn't the topic, it's getting a word in at all. In practice sessions with friends, the same two or three people start talking the second the topic is read out, and by the time there's a gap, my point has already been made by someone else.

What's worked for people here? Some things I've read but haven't really tested:

• Open the discussion yourself if you have even a basic structure ready ("Let's look at this from the student side and the employer side…").
• Enter by building on someone: "Adding to what she said about cost…" instead of waiting for silence.
• Summarise at the end if you couldn't get in earlier.

Is opening actually risky if your point isn't strong? And how do evaluators see someone who only speaks two or three times but clearly? Would love to hear from anyone who's been through a GD round recently.