Her bag will be tight, really depends on what youre feeding on exactly how tight. 36 hours ish she'll appear slab sided (flat body), and her loose belly underneath will be round and tight. The baby drops onto her belly with the muscles loosened, her ligs up around her tailhead will recede, and her vulva will come out of the pelvis area. Look for thick off-white mucous. It'll be thin mucous, then really thick for a few days, then super thin, almost watery. When you see thin again, baby is nearly here. Don't go by milk on a heifer. She'll leak even sometimes 2 weeks before she's due depending on what you feed and her production line.