When buying the tree, check that its needles are firmly attached to the branches. Look at the base of the tree where it was sawn and ensure it is pale. This means the tree is freshly harvested and will last longer than a tree which has been off its roots for a while.
Choose a good variety, such as the cone-shaped Nordmann fir or citrus-scented Douglas fir. They're more expensive than the traditional Norway spruce, but they hold their needles well.
Before you position and decorate your tree, take it out of its net wrapping and place it in a bucket of water in a cool, shady spot outdoors. This allows the branches to settle and rehydrates the tree. Give your tree a vigorous shake before taking it inside, to dislodge any loose needles.
You can't beat a real Christmas tree, but fallen needles and bare branches don't look particularly festive.
Saw a few centimetres off the bottom of the trunk to enable it to absorb more water. You can also score the bark roughly at the base of the tree, to maximise water absorption. If you use a water clamp to hold your tree, make sure it's big enough. Never peel off the bark to make it fit or the tree will dry out – water is only taken up through the tree in the layers just below the bark. Choose a cool spot indoors away from radiators and choose low-heat fairy lights.