I had what I thought was a show a few days before my actual show. If your show is anything like what mine was, you'll certainly know. I freaked out coz it was a massive chunck of mucus (TMI), about the size of a golf ball from memory. I rang my mum when it happened coz I didn't know what was going on at the time. I'd heard about the show but didn't know what to expect. But it wont be long.
Also, for me, I had contractions for the whole day when I had my show, then the following day I was fine, then in the middle of the night my waters broke and I went into proper labour.

I had no blood in my show either which is why I didn't realise that's what it was.