How to prevent the passenger in front of you from reclining without notice?

No, you do not have any right to stop the person in front from reclining, and yes, it's childish behaviour on your part to try to stop them. Everybody on a plane has the right to recline their own seat, and flight attendants can and will enforce this if asked.

You put "rest" in quotation marks, but maybe they really do need to recline: they might be sick, connecting from a 17-hour flight spent next to a screaming baby, any number of things that are really none of your business. I've reclined and slept like a baby on a short-hop SFO-PHX flight... because I just flew in from NRT and didn't manage to sleep a wink.

The one useful thing you can do to create a bit more space for yourself is to recline your own seat.

Lifehacker actually has a post about ways to find out which seats are actually non-reclining, so that you can try and book the seats behind them.

A similar article of theirs shows the (meaner) option of blocking the seat with something like a water bottle.

(from gawkerassets)

There's the aforementioned Knee Defender, as well, but that's where you start getting controversial, and indeed Northwest, American, and Continental Airlines have banned it.

It helps to remember that nobody is comfortable in economy class, tempers are short, and purposefully preventing someone from reaching that little bit of comfort they believe they're entitled to by reclining may cause a response from them which you may not enjoy...

I just came across "The etiquette of seatbacks and elbow room" It nicely answers the OP. I would suggest to read the full blog, but the ettiquete is outlined as follows:

1. Look Before You Lie Back
2. Use Only What You Need
3. Mealtime: Sit Up Straight
4. For red-eye flights: " I say equip planes with a third light next to the "seatbelt" and "no smoking" lights: "Seat backs down.""

The blog then continues what to do if you are the victim of an instant recliner:

1. When the person in front of you leaves his seat, nudge the seat back up a little on the sly. Don't be too obvious -- if he doesn't notice (or even if he does), you may reclaim some of your personal space for the duration of the flight.
2. If the person in front of you blasts her seat back and then proceeds to buck in her seat against your knees, you may need to use similar body English to reclaim some of that space. I'm not encouraging you to become a "seat-kicker," but sometimes you gotta make the case in terms the other guy will understand. If she's slamming against your knees...
3. Politely request that she put her seat back up slightly.

Personally I think this blog nicely covers the issue form both perspective.

I'm much taller than average and in some airplines it's already tight without reclined chairs in front of me. Thus on most flights I keep my legs in a normal position, which already makes it very difficult for the person in front of me to recline their seat. This is enough for most cases. But not all.

Communication is usually the best way out of this. Explain to the person in front of you that you need the space (standing up has helped me convey that message in most cases) and if needed with the airplane personnel. If there's another chair available they're often happy to help you out.

Unfortunately that doesn't always work out either. I was on a 10+ hour flight with a person in front of me insisting on reclining their seat. My legs are really long and the chair was painfully pushing against my knees. All seats were full. I tried to communicate with the person, in 5 languages, without any kind of response, as if they were deaf. The flight personnel was also mostly ignoring my situation, even though they managed to get some response from the person (so they were not deaf).

I finally just put my legs over the chair in front of me, pointing upward, a situation that lasted for more than half an hour, after which the person somehow came to their senses and moved their chair slightly forward giving me just enough space to keep my legs in a normal position.

One thing to do is to ask for a new seat. Some airplanes may have a few "extras," and give you some choice of seats.

Even if there are no "new seats," the fact that you asked puts the airline on notice that there is a problem. If they're at all on the ball, the cabin crew will talk to the other passenger and try to work out something between the two of you.