How do you decide which nostril to use for inserting an NG tube?

Aside from asking about any previous medical history, assess inside the nares with a penlight-one is always bigger than the other making access easier.

Left nostril as it tends to be more aligned with the esophagus.
However, I have inserted NG tubes in both.
I don't like my pts messed up when I do this so I put
A towel around neck/shoulders. Ask pt to put chin more to
The chest so NG tube will not go into the airway.
Give pt a glass of water and straw and tell pt when to
Drink as I in putting the NG tube in.

Make sure to look at the patient's chart first. Knowing if they have any issues with their nose is paramount. Second, you pick which side to start.