I'm going to cover four basic stances. For simplicity, all stances will be described assuming a right handed fighter with a right foot lead. All stances should be practiced with both sides leading.
Basic starting stance
Right foot forward (lead foot) toes pointed at opponent
Feet shoulder width apart, length of stance front to back slightly longer than shoulder width
Left foot (back foot) toes pointed 45 degrees
Right hand (lead hand) at sternum level, blade angles slightly forward towards opponent
Sternum will be pointed around 30 degrees offline
Blade back 45 degrees at most
Bottom hand at jaw level
Sternum will rotate to be pointed more towards opponent
Feet stay same
Many fighters use this guard with good effects. I find it limiting myself, and predictable when facing. Good for set ups and the threat of the big overhead blow.
Open low stance
Lead hand even with upper thigh
Blade angled slightly downward and to the right
Sternum will be forward towards opponent
"Closed" low stance is the same, with the body rotating to bring the point online with opponent
Lead hand level with nose, bottom hand elevated above head
Keep lead hand loose, with handle braced in meaty part of palm in line with bones of wrist, NOT hooked on the thumb
Blade pointed outside right foot and slightly forward
Turn your body to address opponent, don't just move your hands
Strong defense and countering guard- can be jammed if you let an opponent get too close
* Practice stepping forward and back in each stance. When that is smooth, practice stepping forward and back while rotating through the stances.