Here's some tips I've learned from many years of living with cats. Home you find them helpful;
1) Make sure the tree has a solid base to reduce the chances of it being toppled over.
2) Position it somewhere away from things like shelves or furniture which a cat could use as a launch pad to jump onto the tree.
3) Place fragile or ornaments on the higher branches to prevent breakages. Avoid using tinsel as some cats will try eating it.
4) If you're planning to use tree lights, use a cable tidy hose to conceal the wires to prevent your cat from chewing or playing with them.
5) Surround the base of the tree with pine cones. Cats find them uncomfortable to walk on, so the more pine cones the better. You could also spray them with a few drops of a citrus scented essential oil. Generally cats dislike those smells, so they should help discourage a curious cat from wanting to get too close.
Most cats are curious about new items in the home and want to investigate them, so it's a good idea to provide an alternative activity for your cat. Something which is fun for them to play with should make the tree seem less interesting. This web site has some novel toys and you could even buy your cat his own Christmas tree;
http://www.cleopet.co.uk/cat-toys-c-501.html?osCsid=umf2vpdgu1gavg8sk0pcrg08s3