Shave with the grain if you are using a razor. If you are using a rotary electric try switching to a foil electric. Rub the area after you shave with your hands to straighten the hairs. If you don't have acne using an aftershave will do a better job standing up the hairs. Don't rub the crap out of the area just do a pass or two with your hand to dislodge any bent or stuck follicles. I tend to rub perpendicular to the grain but not sure if that is norm. I would imagine rubbing with the grain wouldn't do too much.
I used a pretty old razor a few months ago, shaved in all the wrong ways... was very rough.. zero ingrown hairs or irritation.
Every attempt since then I've been so careful.. prepped my skin.. had a nice blade... ingrown hairs every single time.
I'm forced to use an electric.
The ingrown hairs are always on my neck by the way.