I am taking it to mean in the postpartum care?
What I do is instead of going at it with my fingertips, I use the side of my hand--my little finger side. And I kind of feel with a massaging-scooping motion. It gives a greater area to feel and also, the massing motion helps firm the uterus up a bit and makes it easier to feel. Plus most of my patients say it hurts less that way than with pressing down with the fingers. Start feeling where you expect it to be, U or U-1 etc. Then either move up or down accordingly.
Make sure your patient is flat, because even just a little elevation in the head or back will make the fundus harder to find. And if you really can't find it, have them urinate. That helps too. Even if they don't htink they have to go, they usually can put out some urine. And if they are post-epidural, they may not feel that their bladder is full anyway.