Plotting points on a grid
A coordinate pair is written (x, y): move along the horizontal axis first, then up or down.
A worked example
To plot (-6, 3), go 6 units left of the origin and then 3 units up, which lands in the second quadrant.
The mistake people actually make
The first number is always the across value. Swapping them sends (5, -8) to where (-8, 5) belongs, in a different quadrant.