things you are bad at that everyone else is good at: tips if you have them

If you do not feel like licking your fingers when you are out and about, you can pull one of the corners so it distends the plastic and creates texture to make it easier to open via rubbing.

I breathe on my fingertips as though to warm them -- usually moistens them enough to get the bag open.

(xp) That sounds a bit like the Peter Cook method, as demonstrated on an edition of Room 101, which can probably be googled, and which I've used ever since first seeing it.