Not sure what is new in guidelines. They are repeating more or less known facts:
- acclimatisation (at least one week, experts recommend two weeks, but your milage may vary)
- drink with added sodium (salt) – I still tend to drink when the aid station appears or when I feel thirsty. Although I see more and more recommendations to drink before thirst. Oh, well.
- use external cooling (ice, pouring water …)
- cooling down before and after the event