We suggest you format the card in the below situations,
1. when you use a card the first time,
2. when the camera asks you to "format the card"
3. when the cam behaves abnormally.
You could format the card by the cam itself or by PC,
We suggest you download the GUIFormat tool from the attachment for a deep format. FAT32 is the recommended format for a dashcam card.
below are the cards we recommend,