When using the grid for the rule of thirds, it is important that you make sure characters eye levels are above or around the top line.
When asked to draw out a frame of two characters interacting on the grid, i found i didn't stick to the rule which led to me drawing the characters way too small, with their eye level under the chosen line.
The characters i drew were also too close to each other. This made the situation look too personal, whereas i could have put them further apart to make the situation seem more neutral.
