1. Swimming only in pools
"Make sure you get open-water experience so you feel comfortable on race day," Madison says.
2. Not practicing transitions
Rehearse taking off your wetsuit, getting on and off the bike, and changing from biking to running shoes to make it automatic on race day.
3. Never finding your speed
It doesn't matter how fast or slow anyone else is. "You need to have an idea of the pace you can hold for the distances of your race."