No, the airline won't take half of the points when you book your outbound. In most cases, they will take all of the points for the round-trip award.
Every airline has different policies. AA, for example, allows you to book the outbound portion of the plane trip and "hold" the reservation for 14 days before booking the return. UA, on the other hand, forces you to book the return flights within 72 hours of when you booked the outbound flights or you lose the reservation and have to start all over again.
Thus, on some airlines, you can book the outbound at 330 or 331 days (depending on the airline) and at others, you'll have to wait to book the outbound until shortly before you can book the return flights. The longer your trip will be, the more likely it is that outbound award seats will be gone when you finally make your full reservation.
The good news is that more and more, airlines are making additional seats available well after that 330 day mark. The bad news is that more and more airlines are making few if any award seats available at the 330 day mark.
For those, such as Kathy, who can travel in the off-season, it's much easier to get those off-season award seats.
As to what should the action plan be (ordering the travel package, making hotel reservations and making plane reservations), I would go with
the order that Marriott recommends:
1) Make hotel reservations first.
2) Then order the travel package.
3) Then make plane reservations.
Part of the thinking here is that the hotel space becomes available about 50 weeks in advance - a bit more than two weeks before the airline seats might first become available.
However, if your testing (pretending to make reservations for other dates with likely similar demand) indicates that the hotel reservations are more readily available, I would change the order to travel package first, then plane reservations, then hotel reservations. There is no single best answer to this dilemma.
Note: There are numerous situations that don't fit with my explanation. For example, Southwest flights can typically be reserved only 120-180 days in advance. I have tried to give a general explanation, but you need to call your airline (or check FlyerTalk) to find out what the airline's policies are.
Note #2: Even though I recently linked to this thread, it is a very old thread. The AwardPlanner service referred to at the bottom of my above post is no longer available and there is no similar service that I’m aware of.