Try to select a fresh tree by looking for one that is green. The needle should bend and not break and should be hard to pull off of the branches. One simple test for freshness is to gently grasp a branch between your thumb and forefinger and pull it toward you. Very few needles should come off in your hand if the tree is fresh. Shake or bounce the tree on its stump. You should not see an excessive amount of green needles fall to the ground. Some drop of older, interior needles is a natural and normal part of a tree's growth.
As soon as the tree is brought home make a fresh cut removing at a "maximum of one inch" of the trunk and place the tree in a sturdy water holding stand. If you have a pin stand and the retailer has drilled your tree and you cut off more than an inch, the hole will not be big enough and the stand won't work.
Make sure the stand is kept full of water so that it does not dry out. Avoid small "coffee cup" stands that hold too little water. A stand that will hold a 4-inch diameter trunk should hold at least 1 gallon of water after the tree is set up.
Stand your tree away from fireplaces, radiators, televisions, and other heat sources.
Only use indoor lights on your tree, check lights to see that the cords and connections are in good working order. Be careful not to use more than three light sets per extension cord.
Unplug lights when going to bed or when leaving home.
Research has shown that plain water is by far the best thing to have in the tree's stand. Some commercial additives and home concoctions can actually be detrimental to a tree's moisture retention and increase needle loss. Water holding stands that are kept filled with plain water will extend the freshness of trees for weeks.