Oh you will definitely know when you're in labor. For me, my water broke at home but I didn't have contractions for about an hour... When the first contraction hit though, it was insane! I thought that labor would just be more intense braxton hicks but this felt like extremely bad period cramps and felt like I needed to poo.
BFP 10/1/2010 MMC D&C at 11w4d
BFP 3/15/2011 M/C at 6w
BFP 5/25/2011 DS1 born 1:11pm on 1/16/2012
BFP 10/18/2013 EDD 6/28/2014 GROW BABY GROW!!!!
Cervical checks are not a reliable sign of labour- you can go from 0 - 10 in hours or be 3 or 4 centimeters dilated for weeks. I know so many women who were told they would be going into labour immediately because of their dilation but sat around still pregnant for ages- and vice versa. I wasn't even offered any cervical checks for either pregnancy because the dr/midwife didn't feel they were beneficial, and I even went 10 days late with DS1.
Possible signs of coming labour include losing your mucus plug, loose bowel movements, sore breasts, an increase in BH contractions, spotting/"bloody show," decrease in fetal movement, and the baby "dropping" low into your pelvis, so that you feel like there's a bowling ball between your legs when you walk. However, plenty women don't experience any of those before labour, and probably just as many start to experience those a month or more before labour starts.
Bottom line, though- you will know. Unless you happen to have a very fast labour (which isn't common for a first time mom), I can't imagine you will end up birthing your baby in your bathroom because you weren't sure you were in labour. If you aren't sure, you either aren't in labour, or it's too early to worry about going to the hospital.