With me, it honestly felt like I could have set up a cot in my bathroom because I had to go so much! Sorry if it's TMI, but it's true. Also, I got some ugly stretch marks on my lower pubic mound. I also got extremely paranoid that my water would break, and I was very hesitant about going out in public for fear that this would happen. I had LOTS of pressure down below!
It was a gradual process over the course of about two or three days and I gave birth three days after she dropped. Generally, you'll just feel uncomfortable walking...like you're waddling. You'll know when it's starting to happen because when it was once just "difficult" to get out of bed will feel like it has become impossible!