When Do You Book!

Book when you find a reasonable fair. Just keep checking, sign up for airfarewatchdog or travelocity alerts. For our trip this year we found a great fare 9 months in advance. We bought it and it was gone the next day ($710 including tax Sea-CDG in May). But it's always a crapshoot--there is no general rule, except that as flights are cut back, you don't want to wait too long.

For a trip in June,July , August or September I would book hotel around Xmas time or maybe January. . Just to get first picks of the good budget hotels.I did encounter one hotel that refused to take reservations more then 90 days out. You will get a hotel if you book much later then that, but the good small word of mouth ( or forum) ones fill fast as they often only have 15-30 rooms max.
I also book hotels that I can guarantee with my CC and allow me to cancel up to 48 hrs in advance with no penalty or just a 5 dollar processing fee. I have booked hotels and changed it several times within the months leading up to trip.
I once waited till Feb. to book hubby , his friend, and son into hotels for Paris in June( high season, but so is Sept) ,, STUPID,, all the hotels I wanted to use were full,( triples fill fast) and we had to pay more to put them in another place.

Airfare for this past July I booked in December.
I am now looking to book for an April trip to Hawaii, but I will wait a bit longer for that,, just looking at prices so when I do book I will know if I have paid a fair price..
I am planning to return to Europe next Sept, I will wait till late winter to book airfare, likely Feb/March, just waiting to see how things go.

I'm going in June of 2009, and I already have airfare from USA to Venice, flights from Venice to Prague and all hotels/transfers booked. Start the process as soon as physically possible.

I agree on making hotel reservations as soon as possible (unless they are not refundable). If you have already reserved your space on the R/S tour, the your dates are pretty much already set. American Airlines will only book 329 days in advance, so you are pretty close for that airline. It differs a little with others. With the economy the way it is, and with the way airlines are adding fees and upping prices, now may be better than later -- but who's to say?
Good luck.

I would start tracking air fares about 6-8 months out on sidestep.com. I would try different departure and arrival airports and different dates to get the best price. I would buy the tickets when I felt like I was getting the best deal I'm going to get. I book hotels for arrival night and departure eve after booking my tickets. The rest I do on the road.

Beware lately there has been a rash of canceled flights that can affect your hotel bookings even after you purchase your air tickets.

Sidestep.com and its sister site, kayak.com are good for tracking flights. Just be aware they do not show any flights on American Airlines. You'll have to check those separately.

With the way the economy is now, thinking of buying your air tickets 11 months ahead of time may not be a wise idea. Flights change. Prices change. Airlines go out of business.

When to book is a question we see a lot and there is not answer because no one knows when the best deal will be. I think you'll have better luck during the winter months when airline fares historically are cheaper and they haven't yet priced the summer.

Some like to book flights way in advance, others like to wait. Some like to have all their hotels booked before they leave, others do it as they go. Neither is right or wrong--it's all personal preference.

I would start watching fares, just to get a feel for what reasonable fares to/from your destination will be. But I wouldn't think of booking at this time.
For a London/Paris trip in March of 2006, we booked some time just before Christmas of 2005. I was getting anxious and thinking about pulling the trigger on the direct BA flight from SEA to LHR in the $800/pp range. I had previously signed up for the BA club online and would receive emails for deals. And then one showed up! It ended up costing $813 total for 2 people, after all fees! That was half the price that I was about to purchase.
For our late November 2007 Italy trip, I booked on September 18 - about two months ahead. Again, I had already figured out my preferred airline, using the new SEA - CDG direct flight on Air France. We were open to the in and out cities in Italy, and I spent many minutes of many days trying and retrying different choices to find the best combination. We ended up paying ~$1750 total including fees. I'd like it to have been cheaper, but with the high price of the Euro (around $1.55 USD), and fuel costs, I felt like it was a decent deal.
I'm currently watching airfares for a mid-late trip to Spain and Portugal. We're targeting the British Airways flight into LHR again. We prefer not laying over in the US. To use that airline and then go into Barcelona and then out of Lisbon, I've seen the prices drop to sub-$1000/pp. But we'll also consider just doing that flight into and out of LHR and use regional airlines to get us to and from Spain and Portugal.
It can be a lot of work, but I highly recommend doing research into the many different options and keeping up on general flight costs during the different seasons. If it appears to be too overwhelming, then you may want to find a travel agent to talk to and let them do the work - that is assuming that you find one that will do the work for you. Also, sign up for Kayak's notifications for your destination!

I bought my air tickets in August for my trip in May 09. I also started booking my hotels at the same time. I'm glad I got my plane ticket already as the flight that I booked is no longer available.