First of all, I’ll go on the record right now and challenge anyone else here to a game of online hearts… name a place and time, I’ll bring the hammer 
Some general pieces of advice:
-Assuming that you are playing to win, that is, playing to come in 1st, it is vitally important that you constantly bear in mind the relatives scores of you and all the other players. When you’re low, it’s a raw struggle to survive. When you’re not, it’s a team game, albeit one with constantly shifting teams and no one you can really trust. Remember, if the scores are 20 50 80 80 and you have 50, you really can’t afford for either guy with 80 to take the queen, even if it means taking it yourself.
That said, there are two kinds of hands… those in which you have the queen and those in which you don’t.
Hands in which you have the queen
When you have the queen, life is pretty straightforward. Try to dump it on the appropriate target, or, if there is no target, anyone at all. There are two tricky strategies I will suggest when one has the queen:
(1) If you have the queen and you are the low man, play deceptively. Lead spades from a short spade suit. Fool your opponents into thinking that you’re trying to drag out the queen. (This will only work if your opponents are aware enough players to notice what’s happening).
(2) Aggressively strip out all your entries. Suppose this is your hand:
Clubs: AKJ5
Spades: Qxxxx
Diamonds: xxx
Hearts: x
When you get the lead, the first thing you should do is PLAY ALL YOUR HIGH CLUBS. This may seem odd, but remember, you can’t be punished, you have the queen. Once you’ve played them all, then you can’t be stuck into the leads with clubs from then on. If you ignore the clubs and start doing other things, someone out there will probably have 346 of clubs and just screw you over and over again.
(It’s very nice in a situation like that to have one and only one heart, particularly if the rest of your cards are high. Frequently, I will take all my high cards until I’ve exhausted everyone else in those suits, then lead my single middle heart. If someone takes it, presto, I’m out of the lead. If no one takes it, presto, I shoot the moon. This even extends to having A8 of hearts or something like that… play the ace first, eat the four points, and then lead the 8.)
Hands in which you don’t have the queen
There are two stages to a hand like this:
(1) figure out who has the queen of spades
(2) make sure that it finds a good home
Basically, watch what everyone leads. If someone leads spades, that person doesn’t have the queen. If someone plays lots of high cards unconcernedly, that person probably has the queen. If someone takes the opening lead with the Ace of clubs and then plays the Ace and King of diamonds in quick succession and then the 8 of clubs, that person probably has the queen and is now void in diamonds, because why else would they play two high diamonds and then stop.
It’s a very tough balancing act between covering your own ass by pitching high cards and staying out of the lead, and being aggressive in your pursuit of the low man.
As for shooting the moon, sometimes you’ll just have zillions of high cards and a big heart suit and moon. More often, though, you void yourself in hearts and have a long suit in one of the other suits. This is the best kind of hand to have, because (assuming you have both high and low cards in your long suit) you don’t have to commit to anything until you’ve seen the first several tricks… often you can set yourself up with a good shot to moon, someone else will take a heart, and you can escape unscathed.
And this is why it’s CRUCIAL to always pass a low-to-medium heart, and to not be afraid to take the first heart trick after hearts are broken. (And, in general, if you can take the first heart that is played, for instance on a club trick, you always should, because (a) no one else can possibly moon, and (b) people will be worried about you mooning, even if there’s no chance in hell that you will, and sometimes you’ll get away with total murder because of it)