I wouldn't bother, just carry supplies with you in case it happens. Don't use liners unnecessarily, as that can actually cause more discharge, discomfort and irritation.
Spotting would generally be just very light bleeding, you would probably sense it and will appear when you wipe or on your underwear.
It's not a bad idea to keep some supplies or an extra pair of underwear and/or leggings that you could keep in your bag or locker for emergency situations.