Suggestion: Always go with a bigger tent than you need (unless backpacking), and always set it up several times at home before leaving. Also, photocopy the instructions, and laminate them and keep them with the tent. We got a Eureka cabin tent, and I'm in love with it, but have to admit that there is a learning curve to putting it up quickly and efficiently. Many tents also benefit from labeling or color-coordinating the poles/tabs/grommets, etc.
Bring an extra tarp. Make it two.
Bring extra line for guys.
Bring a sewing kit.
Prep the seams at home with water-proofer to stop drips. Most quality tents now come with a seam prep kit, included. Doesn't hurt to prep the seams once a year.
Make sure your tent is appropriate to the location and season. Here in most of TX, at least three seasons require a tent with a lot of mesh at the top to let out the heat. Get up to Colorado for elk hunting, and you need a solid-topped tent with good supports to keep the roof up even with a foot of snow on it... in early October.
No matter what the weather man says-- prepare for rain. Likewise for heavy wind.
No matter what the box says, you can't put as many people in the tent as are listed.
Even if the tent has a built-in ground cloth, put a ground cloth (tarp) under it. Fold the edges
under, lest you create a wading pool under the tent.
Don't buy exclusively based on features-- execution is all. My wife and I bought a super-nice (we thought) large no-name tent from Wal-Mart that had tons of nifty features... only to have it torn to shreds by a windstorm that night. Fortunately, we still had our receipt, and got our money back and bought a quality name brand tent the next morning. But that night was miserable!
I'm a big fan of well-made dome tents, but have only had good luck with them on the smaller scales-- 2 to 5 man. If you really plan to never have more than 2 people in the tent, you can make do with a 3 man tent, but don't go smaller. 2 man tents are great for two Boy Scouts who aren't afraid to rub shoulders and don't mind leaving all of the rest of their gear outside. Me, I'd rather bring the non-food items in with me.