I live in a semi-desert and regularly ride in temps over 90degF in summer.
Yes, acclimatization definitely helps, but regardless
* Drink lots, obviously. That you are drinking lots is much more important than what you are drinking lots of, but avoid alcohol and caffeine. Many folks around here like the Camelbak types of reservoir because they make drinking regularly so easy.
* Cover up. Don't be frugal with the sunscreen. A high factor sunscreen, in addition to protecting your skin, will help you feel cooler.
* You can get enough salt if you just eat plenty of salty snacks, but there's no harm in supplements, either. I habitually take an Enduralyte capsule every couple of hours and unscientifically believe it probably helps.
* Wetting head and body certainly feels good and probably helps if you're already over-heating but it's not a preventative because in high temps it's impossible to stay wet. Better to concentrate on hydration. Having said that, I wear a bandana under my helmet and wet it when spare water is available.
* Learn the signs of heat stroke in yourself and others. It's potentially life alteringly dangerous. Confusion, nausea, shivering, lack of sweat, uncontrollable rapid and shallow breathing, pulse that won't drop, all-over red flush - any of these can be a danger sign. Get to a cool place, drink small sips continually and get urgent medical help if symptoms don't improve very quickly.