Advance booking...but how much?

As long as you have a day or two at the end of your home stay, you get to any of the major hubs pretty cheaply. If I was in your shoes, I would just book the tickets when you see something that is cheap and works for your other non-homestay adventures and then figure the rest out later. It is pretty easy to get around Europe, for the most part and with a few days at the end, you could explore a new city and then fly home. I think you are right that the next month will have the best deals for you getting over there, so I wouldn't wait until January.

Anna, if you fly into Paris you will find it's like the center of a wheel in terms of train connections. Once you know your destination in France, you should have no problem getting there from Paris. From your post it doesn't sound like you're sure when your homestay program begins, and you mention that you've applied to do it, but have you been accepted? If any of this is still up in the air, you'll need a ticket that you can change or possibly have refunded if you buy before January.

Thanks guys, you've been very helpful. Zoe, that is correct. I have not yet been accepted (although I don't think that should really be a problem...) and the date I put on my application was February 4th; however the coordinator told me that sometimes families ask if you can come a day or two later. Thing is, as I said, I'm flying to Spain to begin with for a couple of days...so really if I have to spend a few extra days with my friend or toodle independently around France for a couple extra days, I'm not really that concerned. It's mostly the return flight that I want to be sure of, since I want to visit a friend in France after I'm done my homestay. Do you know if it is possible to buy tickets with a change/refund clause when using momondo.com or expedia etc?

You really need to be accepted into the program and have set dates before you purchase your tickets. They have empty seats on airplanes in the winter. When you say you're going to fly into Spain, remember that it's a very large county. France is too. Getting to small cities from any city other than Paris may just not be worth a 2 day visit.

When you are about to buy your tickets, there is always a way to check the terms and conditions. Most, but not all, tickets do have a change clause: If you give them a call, they can change your ticket for a fee (this can be a couple hundred dollars and usually no less than $150), plus any difference in fare. There are fully refundable/changeable tickets, but they are often double or triple what you pay for a basic economy fare. In my mind, I would take the earliest start date and the latest end date, add a couple days on both sides and buy the tickets. In that situation, the worst case scenario is that you end up bumming around France or Germany or wherever for a couple extra days or a week. Quelle horreur!

You have all been extraordinarily helpful, thank you all so much. !! I received my acceptance to the program this afternoon! They have confirmed my dates as February 4th to April 1st (there is the slight possibility that there may be a one or two day difference on either end, but I'm not horribly concerned about that), though I won't know the exact location in France for another few weeks. Before heading into France, I will be in Lleida, Spain (it's an hour out of Barcelona by AVE)...do you think I should leave two days for travelling out of Lleida, just in case, or if I leave from Lleida on the 4th Of February to get to wherever I need to be will that be enough time? I ask because one of you pointed out that France and Spain are large countries, and I would like to have at least three days with my friend since I haven't seen him in ages...

I would say be sure to get to France in plenty of time, you don't want to start this experience by showing up late. Leaving Spain on the 4th and getting to Paris on the 4th won't be enough time, I'm afraid, unless you get a really early flight out of Spain. I'd plan to arrive in Paris by the 3rd and get as close to your destination as possible.

OK, good to know...so you think flying to Paris and then taking a train (or whatever) would be better than trying to get to my destination from, say, Barcelona?

Give yourself the extra day. If you find that you need it, then you have enough time with your friend. If you don't need it, then you have an extra day with your friend. You will have to see where you are. Buy your tickets to/from Europe and then worry about getting around Europe when you know a little more. Suppose you are in Toulouse: It would make zero sense to fly to Paris to then take a train 3/4 of the way back to Barcelona.

Thanks Nicholas. I slept on it, and since I've now had two people tell me the exact same thing (which was also something I was thinking...) I believe that is what I will do. You guys have all been extraordinarily helpful and I thank you so much :) I may be back... ;)