Pick Your Poison. Define your tent needs and know the features you want before shopping. If you expect to be doing high-mileage trips, weight savings is a prime factor. If you often encounter wet weather, look for a rainfly that reaches all the way to the ground.
Bring Big Jim. Bring your gear and your hiking partner to the store to see if you all fit into your chosen tent. Borrowed gear and partners often have different dimensions.
Practice pitching. Set up the tent. If the tent is already pitched when you walk into the store, take it down and pitch it again to see how easy the setup is. Now imagine doing it in driving rain and wind.
Build your house. Lie down inside on sleeping pads. Figure out where your boots, pack, and wet gear would go. Is the weatherproofing, entry, ventilation, and living and gear-storage space acceptable? Rehearse a midnight exit to answer nature's call. Subtract points if your knee clobbers your partner's jaw.
Say no to sagging. With the tent pitched, check the rainfly's fit. A quality rainfly fits snugly on the tent's pole structure, producing taut panels of fabric that won't flap noisily or act like sails in windy weather.
Quality control. From inside the tent, look over the fabric and seams; the store's ceiling lights provide good backlighting to find flaws. Check for loose threads, stitching glitches, fabric irregularities, and discoloration.
Look for leaks. Inspect all the tent's stitching. Look for bits of fabric, thread, or wrinkles under the taped seams that will cause leaks. Scratch any seam or tape that appears loose to see if it separates.
Mimic the wind. Stress test critical junctions that can cripple your hike if they fail in gusty conditions. Tug on guypoints, stake webbing, and pole-attachment points to see if seams begin to separate. Check that pole end grommets are secure. Inspect zippers for excess tension.
Check the coating. You should be able to see the shiny, waterproof coating on the inside of the rainfly and floor. If you can't see and feel it on the fabric, it may not be thick enough to stand up to heavy use.
Pick the right color. Check how well the tent's color transmits light to the interior. Some colors create a bright interior, while others make for a dreary, cavelike ambience. Light colors are cooler in the summer, while dark colors absorb solar energy, making them better for cold weather.