I tend not to delete anything, but use LR's flagging (pick) feature to identify keepers following a rating session where I have a slightly arbitrary scoring system. A nice shot gets a 4 star rating, an exceptional one a 5*, a nice or exceptional shot that is in effect duplicated or similar or great but not the pick! gets a 3*, or no pick flag and 4*, a technically ok, but meh shot gets a two, and obvious technical issues (oof, camera shake, awkward crop that ruins the image) gets a 1*
Storage is cheap, so I tend not to delete though often do the 1* as I go. However, it's trivial for me to at some stage filter on 1* and delete them all. Everything else would stay. I've often found shots that I've come back to that I'd underestimated, or for some reason (eg a tiny bit of photoshop) can be made great and I had no other 4 or 5 star shots of that image in the set. One of these days I might get more ruthless with my garbage. But I am extremely ruthless when I select my very best images. Generally no more than 1, exceptionally 2 of a similar shot allowed.