Hold your line, be predictable, if you choose to let the faster riders by, do so smoothly, and don't just cut left to get out of the way. If you get mud in your mouth, remember that spitting it out will only make a mess of the inside of your helmet. Oh, and there was this one little jackass at the track today that wouldn't get out of my way, I would leave the main line to get around but that line was too slow, it was only practice and I was obviously faster than him, but he was all over the track. Don't be that guy, if someone is so clearly faster than you, and making the effort to go wide, or cut inside, don't be all over the track, just get off of the throttle for a second wherever it is convenient and let him/her go, but above all hold your line and be predictable.