Have a hydration plan and a nutrition plan in place (if skipping hydration/nutrition early works for you then go with it. If that doesn't work, or if it's a particularly hot/windy day -- definitely don't skip early hydration).
Understand that your plan is subject to change, and it probably will change slightly during the race. Stations are run by volunteers. Some may not be located exactly where the RD said they should be. Some may not have what you expected (RD said station 13 would have electrolyte, but electrolyte did not make it to that station for whatever reason. Some will provide ridiculously watered down sports drink while others will provide grossly over concentrated drink). Some will be run by five year old kids with parents that are not paying attention. Just be prepared roll with it.
Obviously know what the race intends to provide and train with it. Also be prepared to use the delivery method the race uses (Bottle/paper cut/plastic cups, etc.).
Be prepared and cite the stations you will be using in advance, and slowly position yourself accordingly. With the few exceptions, most people will let you slide in the grab what you need. Make your intention known and thank the other runners for letting you slide in. Be mindful that some water stations are crowded and you need to be alert to tripping and other folks grabbing what you were going for.
Don't exert a ton of energy at the stations. You'll have to slow down at some stations. Don't use an unnecessary amount of energy regaining your position or pace. Gradually fall back into your rhythm.
Do not be a jerk to the volunteers. Vent your frustration to the RD later, but don't take it out on the volunteers even if they mess up.
The stations are run by volunteers. Don't be the dick that throws his garbage 800 meters from the garbage or the dick that admonishes the five year old kid who's not paying attention.