In a crit you are either moving forward through the pack or backwards through the pack ... even if you are holding a wheel you need to focus your attention at the front of the field not necessarily your current position. Also, you don't want to be that guy that comes up the inside and takes everyones line away in the corners so be mindful of where you make up position. the best thing to do is to follow all the wheels that move forward all the time, don't sit on a wheel; always pick a wheel that moves forward through the field.