The best defense against ticks are your clothes. Ticks hang out on the ends of branches and blades of grass with their arms in he air waiting to hook onto anything that has blood to pass by. After they hook onto someone/something, they climb up until they find a nice spot to dig in, like under your shirt on your lower back, on your neck, or in your hair. If you don't give them an opportunity to get under your clothes to your skin, then they'll typically get spotted by one of your buddies while they're climbing all over you looking for a way in. It's important to do tick checks too; whenever you stop, take time to look each other over and make sure there aren't any ticks crawling around each other.
As for the way you dress, the best tick and bug defense is tall socks, long legged pants, long sleeve shirt (tucked in), and a hat. Make sure you wear light colours so you can easily spot ticks on your clothes. You can get extremely lightweight and breathable hiking pants and shirts that help you stay cool on hot days.
There are also tick-repellents you can spray all over yourself and your clothes, DEET will work to a degree, but there are other repellents and treatments for your clothes that claim they'll kill ticks after 30 seconds of being on you.
Your first line of defense is always going to be the way you dress, the next line of defense is going to be doing regular checks for ticks, especially after you push through some bush, or brush up against any grasses or other vegetation ticks might be hanging out in. I picked 17 ticks of my wife once after sitting down next to a river beside the wrong patch of grass, so just be mindful about it and you shouldn't have a problem.