The Purchase
Buying a dehydrator is going to be an investment. In fact, I'd look at it the way you look at purchasing a major kitchen appliance. After doing plenty of research about what I'd like to use to make an entire season's worth of hiking meals I chose a 5-Tray Excalibur system with a thermostat. The thing about dehydrating backpacking meals is that you aren't throwing them all in at one time. First, you're dehydrating the mixed vegetables for a few days. Then maybe you're doing rice for a few days. Then, you might be doing a few batches of sweet-flavored rice. You do everything in parts before assembling the meals. Having a fan and a thermostat will help ensure you're dehydrating fruits and veggies at optimal temperatures to keep nasty bacteria at bay. Meat, fruit, veggies - they all have optimal temps for pulling out moisture. The thermostat will definitely make sure you're drying your food at the safest temperatures.
While there are cheaper countertop models of dehydrators available, I definitely recommend going with a model with a fan for air circulation. The round tray systems need constant babysitting to move the trays. If you don't do this in a fan-less model, you'll have leather-like layers closer to the heat source whereas your top layers might not even be halfway dry. You can definitely do months' worth of food on one of these budget models, but be sure you have the time to dedicate to rearranging the trays.
Finally, you'll need a set of fruit leather trays for your dehydrator. You can again go the budget option and use parchment paper. I went with the generic fruit leather reusable inserts on Amazon. I've reused them countless times for the past three years and they don't hold flavors and just need a quick rinse. I highly recommend them. Aren't planning on making fruit roll-ups? That's fine - neither did I! But, you'll need these guys to dry sauces, veggie paste, even condiments you'll want to dry to make them more potent. Trust me, you WANT these tray inserts!
Techniques
So you've purchased your dehydrator and you've found a couple of recipes you want to try out. Maybe you want to try and recreate one of your favorite pasta sides at a fraction of the price you'd pay for them over the period of a distance hike. Either way, it's time to start dehydrating.
Rice
Let's say your recipe calls for you to use your own dehydrated rice for a savory recipe. Instead of just making plain rice like you'd make at home, I highly recommend seasoning the rice before you get it into your dehydrator. If you're making a savory dish, I recommend cooking your rice in chicken, beef, or vegetable stock and salting it slightly heavier than you would eat at home for a normal meal. On trail, you'll wish it had more salt! After the rice cooks, cool it to room temperature before dehydrating. Making a sweet rice - maybe for a pudding or breakfast treat? Try cooking it with vanilla almond milk instead of water! When it comes time to dehydrate your rice, spread it out thinly and try to avoid clumps of rice. Clumps will hold more moisture and take longer to dehydrate. If you're home while it's dehydrating, go out and break up the chunks of rice every so often to help it dry out faster.
Vegetables
Not all frozen veggie mixes are created equally! My favorite store, Aldi, has mixed veggies in a bag as cheap as $0.95! However, their mixed veggies aren't all the same size and, in fact, the carrots are in rounds that are easily four times the size as the other vegetables. This doesn't make for fast dehydrating OR rehydrating! On the flip side of this, Wegmans makes a great mixed veggie blend with the exception of the lima beans. Lima beans are another rehydration nightmare. I don't care how long you soak or boil lima beans - they never seem to fully rehydrate properly. When you're looking for mixed vegetables to dehydrate for additions to your meals, I highly recommend looking at the contents and shapes of the veggies in the bag. BJ's Wholesale has great 4-lb bags that require minimal changes. The only thing I did to these was cutting the green beans in half to make everything the same size. When it comes to vegetables, uniform size is key to getting them dehydrated and rehydrated at the same times. Trust me, there are few things sadder than being hungry on trail and crunching into half-rehydrated corn when the rest of your meal is ready!
Something I did for our meals a few years ago was broiling and blackening bell peppers before dehydrating. This little something extra really made the flavors taste even more homemade despite being in the backcountry. My most important tip is to NOT mix different veggies in your dehydrator at the same time if you can help it - especially strong-smelling veggies. If you want to do a tray of red onions, put them in by themselves or else all your food will taste like onion!