I usually use 1 part = 1 cup.
1 Part Regular Cheerios
1 Part Honey Nut Cheerios
1 Part Flavor Burst Goldfish
1 Part Raisins
1 Part Cashews
1/2 Part M&M Candies
1/2 Part Reese's Pieces
Some other ingredients I have heard people adding are honey roasted peanuts, Chinese noodles, Pretzel Goldfish, Pecans, Wheat Thins and dried blueberry's.
There are a few ingredients I suggest you NOT use. The first is sunflower seeds. We tried them in our mix because they sounded like a nice salty addition but the seeds are so small they all sink to the bottom of the bag so they won't stay mixed very well. The next is dried cherries. The cherry taste WAY overpowered anything else.
Play with this mixtures and also play with the timing on how soon before a trip you can make the mix. With my mix, I usually make it the day before a short trip. The Cheerios start to soak up the moisture from the raisins. If we are going on a longer camping trip and I need it to last longer, I make the mix without the raisins and bring the raisins in a seperate bag. When we head out for fishing or riding, I mix some of the trailmix and some raisins and put it in a seperate baggie.
Let me know some of your ingredients, mixes and tips.