When scanning a planet, do not hold the LT. Instead, tap LT rapidly until you see a blip on the scanner. Then, go back over the area holding LT to find the best location to send the probe.

Move the pointer to the left or the right of the planet you want to scan. Press the Left Analog-stick and Right Analog-stick in the same direction to double the spin speed of the planet. This allows you to locate resources on the grid line quickly.