Qantas Booking ?
 

Qantas: Considering booking for April 2009. However it appears you can’t select seats at booking.
How can I ensure I get 3 on the side instead of stuck in the middle. Plane is the 747-400 which is pretty tight in economy if your stuck in middle. Any ideas?

Try to ask this question on FT's Qantas board - they'll have the answer.
Don't be afraid - sometimes they can be cruel & rough on a "newbie" on FT.

Did you try calling after booking? I recently booked a flight with Continental FF miles on Virgin Atlantic. They were very helpful when I called and allowed me to pick my seat assignments.

And I get free alcohol with Virgin but Continental would have charged me.

As soon as you book, call Qantas and request seats. If they aren't booked, they will enter your request. I've never been bumped from my seats.

I pay to be a member of Qantas Club so that I do have some priority otherwise you can't get seat allocation before checking in. Sarvowinner has been very lucky.

You can't request exit row prior to check in, but there is no restriction on requesting seats.

My duaghter is bronze and not QC and she has requested seats on her NYC-LAX-SYD flight for next May. se it isn't guaranteed.

Speaking of being bumped - my husband was bumped back a row on CX last week.

The Qantas website indicates that if you aren't a Qantas Club member or don't have elite status with a Oneworld partner (like American Airlines), you can express a seat preference on booking but won't be assigned a seat until check-in.

I've had to fly a few times (mostly Air France) in Economy when I couldn't choose a seat before check-in. I haven't had a problem to date getting an aisle seat. If you check in as early as possible, it's unlikely that you'll get stuck with three middle seats (your question is unclear but it looks like you're talking about booking three tickets).