1) first - concentrate on logging nutritional intake until it is second nature. (Take the time whether in a marathon or over several days - no problem.) I usually log it several times a day so that I can adjust the later meals and snacks to balance the day as best practical.
2) second - learn the logging system for aerobic conditioning and/or strength training, etc. and keep it up each day. (Learn it and use it EVERY day!)
3) third - chasing SparkPoints leads one thru the site very well.