Make a post to your diary. The post should contain your list of 10 holiday wishes. The wishes can be anything at all, from simple and fandom-related ("I'd love a Snape/Hermione icon that's just for me") to medium ("I wish for _____ on DVD") to really big ("All I want for Christmas is a new car/computer/house/TV.") The important thing is, make sure these wishes are things you really, truly want.

If you wish for real life things (not fics or icons), make sure you include some sort of contact info in your post, whether it's your address or just your email address where Santa (or one of his elves) could get in touch with you.
Also, make sure you post some version of these guidelines in your diary, or link to this post (it'll be public) so that the holiday joy will spread.

Step Two

Surf around your buddy list (or your buddy's buddies, or just random journals) to see who has posted their list. And now here's the important part:
If you see a wish you can grant, and it's in your heart to do so, make someone's wish come true. Sometimes someone's trash is another's treasure, and if you have a leather jacket you don't want or a gift certificate you won't use--or even know where you could get someone's dream purebred Basset Hound for free--do it.

You needn't spend money on these wishes unless you want to. The point isn't to put people out, it's to provide everyone a chance to be someone else's holiday elf--to spread the joy. Gifts can be made anonymously or not--it's your call.