The easiest and quickest method of dehydrating food is to use a dehydrator. This is what I recommend and always do personally.
The most energy efficient way is to sun or air dry. Air or sun drying works best if you live in a dry climate with lots of hot days. However it would only be for fruit, sun drying vegetables and meats is not recommended. Please don't attempt drying meat with the sun ever. This would be high risk. I'd recommend keeping to drying vegetables and meats in a dehydrator or the oven.
I don't have any experience drying items in the oven. It seems to me that it would be very inefficient. If that is all you have and you are just dehydrating in small amounts, it does work.
Complete listing of my Dehydrating Food Articles:
The more evenly you can make your slices of food, the more evenly the food will dehydrate. These are my favorite tools to use.
A mandolin slicer (on top), an egg slicer (to the right), and a gadget I picked up somewhere and don't even know what it is called (to the left)! I call it my "tomato slicer" because that is what it works best for. The egg slicer works for soft items like strawberries, but not too much else, as the wires will bend if your food is too strong. The mandolin is best for firmer items like zucchini or sweet potatoes.
And finally, always have a good sharp knife. I forgot to get that in the picture but... surely you know what a knife is, right? Having it sharp is essential as it is actually less likely you will cut yourself with the knife nice and sharp. In addition, a sharp knife will be more efficient for cutting nice thin, even slices.
My absolute favorite finds as far as kitchen tools for dehydrating goes is this little pot.
The 4th Burner Pot has turned into a handy tool that I use to slice up my fruit and drop it into lemon juice before laying out on trays.
I have a full review here.
Other popular dehydrators... is yours listed here? Tell us what you think. Help others know what to get or... NOT get.
The most recommended dehydrator on the market is the Excalibur.
I personally have a commercial dehydrator from Cabela's.
Nesco Food Dehydrator is one of the leading names in food dehydration and has been for more than 30 years.