Sleeping under the stars is very romantic. The smoke from the campfire on the breeze, the buzzing of the insects, the gentle kiss of the rain...but tents are nice, too. A little bit of shelter can go a long way toward a good night, and a well-rested camper is a Happy Camper.
Every indigenous culture had some form of portable or temporary shelter, but few of them were light, durable, convenient, or truly comfortable. Canvas was the material of choice until the development of durable nylon and polyester fabrics in the 1960s, and when the first 'dome' or freestanding, tents were introduced in the 80's, backpackers everywhere rejoiced.
Types
Tents can be generally grouped into Backpacking or Base Camp styles. The former will prioritize weight conservation and efficiency of design for up to four people, and be used mostly for sleeping, while the latter will be much larger and heavier, with room perhaps for cots, a table, and walking around inside. Family Camping and Hunting both favor base camp tents.
Ultralight hikers will rarely pack shelter in the form of a tent. Instead the minimalist will have a tarp strung between trees or staked out with their trekking poles providing structure. A ground sheet will be separate and the ends and sides are open for ventilation.
The primary goal of any good tent is to provide comfortable shelter. Most backpacking tents are described as 'three season,' for conditions ranging from high wind, steady rain, and chilly air through still, sweaty nights swarming with bugs. 'Four season' tents are really best used in one season - winter, since they have reduced ventilation to preserve warmth and heavy-duty construction to handle storms.
Comfort is achieved by balancing weather protection and ventilation, usually with mesh panels on the tent body and a separate rainfly that prevents water from entering but allows air circulation. In favorable weather, the fly can be removed so maximum air movement is available but the campers still have a clean space without bugs.
Freestanding vs Stake-out
The majority of tents sold today are freestanding, meaning they don't need stakes or tensioned guy lines to stay up. This means setting up and moving your tent is much easier, and it will fare better in windy conditions. You can still find stake-out designs at the ends of the weight spectrum, where some other consideration is more valuable. Ultralight tents will frequently be stake-outs to reduce the length and weight of poles used, and very large basecamp tents with more vertical wall space and heavier materials require a different pole design that has fewer tension arches.
Clip vs Sleeve
When the first freestanding tents were introduced, the pole slid through a cloth sleeve and anchored in a webbing pocket at each end. Modern designs will frequently use plastic clips in place of the sleeve, even though the sleeve design is lighter and stronger. The process of setting up a clip-style tent is much faster and less frustrating, and a broken clip is easier to work around and/or fix compared to a ripped pole sleeve. Less expensive tents will still use sleeves, or they may be part of a clip design for additional strength.
Single-Wall
A rainfly is the best way to provide weather protection and ventilation to the occupants of a tent. Acting like an umbrella, the fly also makes sure the dripline is away from the floor and/or groundsheet. For some conditions, however, you might want to lose the addtional weight and complexity and use a single wall design. Best suited for cold and dry conditions, these tents will have fully windproof/waterproof construction with much less ventilation than a double-wall tent. The weight savings can be significant, but in mild conditions the lack of air movement through your shelter can make sleeping a chore.
Comparing
The overall weight of a tent is an important specification, and lighter materials that don't compromise performance are more expensive. The best example of this is the poles, where carbon fiber can be used to replace aluminum, and can weigh less than half, but may cost three times as much.
Fabric selection also makes a big difference in the weight and cost of a tent. The widespread use of lightweight silnylon has changed the definition of a lightweight tent to under 4lbs for two people. When comparing tents in a similar price range, remember that the weight listed is determined by the manufacturer, and they know you will be comparing ounces. When determining the real carry weight, It's best to add 4 to 6 ounces for a groundsheet and extra stakes you'll end up bringing along.
A very light two-person tent is designed to fit two sleeping pads and bags and very little else. As the weight increases, you may see more floor space, frequently described in square footage. If you (or your mate) are over six feet tall, however, it's important to check the actual dimensions of the floor and make sure to have a couple inches for foot- and head room. Some campers are willing to carry the extra weight and upgrade to a three person size, which might not be longer, but will be wider to accomodate gear, elbows, or just room to move.
Deciding
When you start shopping, the tents will all look very similar, so take a good look at the best-selling tent in the size you want but one price range up from what you want to spend. Chances are you will find some version of the design and best features on lower-priced tents because the gear market recognizes good ideas and tends to adopt them widely.
Key features to look for will be a rain fly and tent floor made of coated fabrics with sealed seams, aluminum poles with integrated ferrules, and some form of color coding for poles and grommets. Climb around inside and see which has enough space inside so that when an overnight shower takes over the next day, you won't get a cramp trying to move around inside your tent.
You can find a halfway-decent tent for about $150, or something you'll use for years in the $200-300 range, or get less weight and more performance above $400. The difference will be in the details of materials and construction - poles, fabric, design, features. Because tents rarely sell due to 'brand appeal,' the price will have some technical explanation.
Keep it longer
Protect the floor of your tent with a waterproof plastic barrier or groundsheet made from a shower curtain liner or 4mil plastic sheeting from the hardware store. By keeping the tent material clean and dry, it will require less maintenance and last much longer. The manufacturer may offer a 'footprint,' which is exactly the same as the floor of the tent, complete with webbing and grommets, and is essential if you intend to use the 'fastpack' option with just the poles, fly, and footprint. However, the expense and weight are much greater than a piece of trimmed plastic sheeting that can be replaced easily when it wears out.
Leave your shoes outside the tent, unless you are a dog, who should wear shoes on the relatively thin floor material. By keeping abrasion and dirt to a minimum, the material and seams will last for years.
Tents can get sunburned, or more accurately, the nylon used in the fly can be damaged by UV light. This bcomes an issue when the tent is left up for an extended period and/or at upper altitudes. Most backpackers make camp in the afternoon and pack up in the morning, so a roasted tent is pretty rare. If you do plan to leave your tent up for a few days, find a shady spot, and don't make it a habit. For extended basecamp tent living, canvas is an excellent choice, since it is highly resistant to UV rays.
Glossary
Ferrule - Joint where two tubular sections join. Found on tent and trekking poles, can be a weak point or strengthening element. Standard ferrules will use a separate piece fitted inside the tube and secured. Integrated ferrules will expand the diameter of the end of one pole to accept the other pole end.