Needless to say, you shouldn't use Valentine's Day as the only day to tell someone 'I love you', be it lover, friend or family. I've always had a hard time communicating that to people who weren't immediate family, and sometimes even them, so I need to remember:
If I call you friend, if we've shared sorrow and joy, tears and laughter; if we've fought but not let that destroy our friendship; if I've cooked for you and you for me (lavish dinners and broiled cakes, all); if we've dropped everything at a moments notice to run for an emergency (burned hand or broken hearts); if we've bought dinner or drinks or whatever Just Because; promises of couch space, time, phone calls when they're needed most - space, when it's needed most; if we've laughed over things no one else would get (anime drinking games and roommate tales); if we've been together even when we've been apart ...
Then know I love you.
(Copy and pasted from FB, just because I'm that lazy.)