You can give one tip, and only one tip. What is it?

Blister prevention is everything and dealing with hot spots on your feet before they form is probably the biggest issue. I use a lot of moleskin and athletic tape but getting some miles on your feet in your boots is the best solution. If I start out and immediately get an area that is rubbing, I stop and fix it. A too-lightweight of boot will hurt you too, not enough ankle support or a too-soft insole that you get bruising injuries from stepping on pointy rocks. Best advice, wear and walk in your boots as much as you can before your trip and most of those kind of issues will be sorted. I've got about a 100 miles on my boots since January and my boots and I are just finally coming to terms.