Weight is always a top consideration for backpackers. Purchasing an ultralight shelter should involve comparing weights and keeping weight to a minimum. Beware that not all weights are created equal. You'll find a variety of weights listed, but the one you want to pay most attention to is packed weight. This figure indicates the heaviest that the tent will be and includes all of the tent materials and packaging--essentially what you'll actually be carrying if you use the entire tent as designed. Other weights, such as minimum weight, are useful if you intend to modify the tent and only carry certain pieces. Good backpacking tents should maintain a packed weight of 5 pounds or less for a two-person tent. The lightest two-person tents will weigh just more than 2 pounds. Bear in mind that if you intend to use a tent for several people, the packed weight can be divided among those people, as you can split the tent parts up. Generally, one two-person tent will weigh less than two one-person tents, so opting for a larger tent and splitting up the tent parts is a good way to reduce packed weight.
Packed size is another important consideration when you'll be carrying the tent on your back for miles on end. You want a tent that compacts down and fits easily into or onto your backpack. Pay close attention to the packed size dimensions and consider how well the tent will fit your pack.
Backpacking tents are notorious for having exaggerated ratings for the number of people that will fit. A two-person tent probably means two small people that don't mind cuddling while leaving their gear outside. You can largely ignore the number of people. The best way to size out the tent is to pitch it before you buy it. Consider the size of the people that will be sleeping in it and how much gear will be stored in the tent. In many instances, you may want to buy a size up (such as a three- or four-person tent for two people). Ensure that the length of the tent is enough to allow you to lay down comfortably.
Backpacking tents that use a significant amount of mesh provide good ventilation. Many backpacking tents use single-wall design, in which one wall provides waterproof protection without the need for a rain fly. Single-wall tents are quite light, but they tend to have limited mesh and provide very limited ventilation, sometimes causing condensation in the tent. If you opt to save weight with a single-wall tent, be sure to verify that it has sufficient ventilation. Alternately, a double-wall tent that uses an exterior made largely of mesh and then a separate rain fly for inclement weather will provide good air circulation and maximum comfort. You'll want space between the rain fly and tent body to provide air circulation. Some tents include a rain fly with vented hood for additional ventilation. On hot, clear nights, the rain fly stays in your pack and you're as cool as you possibly can be.
Backpacking tents come in a variety of styles. Some tents eliminate the poles and require that you use guy lines to erect the tent. Other tents are freestanding and use poles to create tent structure. Determine the tent design that will best meet your needs.
Some additional tent features to keep in mind include factory-sealed seams to prevent leaks and save you time, a tub floor to provide good water protection, and separate doors to quickly exit the tent and avoid crawling all over your buddy. Additionally, a vestibule is good to keep gear out of the tent but protected from rain, and purchasing a separate footprint will go a long way toward protecting the bottom of your tent.