In regards to using the RailEurope website I wouldn't purchase tickets from them unless you have first compared prices with http://www.voyages-sncf.com (in French) or http://www.tgv-europe.com (in English). Depending on your country of origin they don't always show all available trains and can charge higher prices. I'm not saying don't use them, I'm saying compare with those other sites before you do.
For trains requiring seat reservations (all TGV trains and some Intercités trains) you need to book up to 3 months in advance for the cheapest prices. Some routes can be booked even further in advance.
If you use the website http://www.tgv-europe.com for schedules and prices. Don't forget to uncheck the box marked "Direct Trains" to see all possible options. If the TGV site redirects you to the RailEurope website then try again and enter Great Britain or Antarctic as your ticket collection country. Other countries may also work but just try to find a country that doesn't get you redirected to RailEurope. The RailEurope website often doesn't show all the trains and generally has higher prices but you can check just to compare. For trains that require reservations you can buy tickets up to 3 months or more in advance and the earlier you buy them the cheaper they will be. The discounted tickets are known as PREM tickets but these are non-refundable and can't be exchanged.
Here is a website that will tell you how to navigate the TGV website:
http://www.nickbooth.id.au/Tips/FrenchTrain.htm
An excellent website to learn all about train travel in Europe is www.seat61.com.
You only need to buy tickets in advance for those trains requiring seat reservations. For the local trains (known as TER trains) you don't need to buy in advance as the fares are fixed and trains can't sell out.
Look at this link to see a map of where the regional and long distance trains go in France:
http://www.bueker.net/trainspotting/map.php?file=maps/french-network/french-network.gif
To see maps of the local train routes for each region go to http://www.ter-sncf.com and look at the map of France in the upper right corner and click on the region that interests you. Once you click on a region scroll down and look on the lower left of the page in the column that says "Se déplacer en TER" and in that column click on "Carte du réseau TER" and you'll get the map of the local train routes in that area.
Trains won't get you everywhere you need to go so you should get acquainted with the local bus routes. The sites you're most likely to visit are scattered in three départements (administrative districts) called Loir et Cher, Indre et Loire and Maine et Loire. Here are the websites for the bus networks in those regions. They're in French only but google translate can assist and figuring out at least dates and town names shouldn't be too difficult:
http://www.tourainefilvert.com/
http://www.transports-du-loir-et-cher.com/index.php?recherchez-votre-itineraire
http://www.anjoubus.fr/
If you go to the Tours tourist office website you'll notice they offer several day tours that are reasonably priced and you'll see a lot more in one day going on one of these excursions than you could on your own using public transport. Here is the weblink for the Tours tourist office. Click the tab on the left that says "Excursions" and you'll find all the info you need.
http://www.tours-tourisme.fr/index_en.php
If you'd like to go cycling there are many bike trails in the Loire and there is a website you can search for all your cycling needs in the Loire:
http://www.cycling-loire.com/
To figure out what to see and do in the Loire look at the tourist office websites. Every town and village in France that attracts tourists has one. Click on the link to the thread below and you'll get the links for all the major websites in this area:
http://www.fodors.com/community/europe/france-the-loire-valley-in-conjunction-with-the-tour-de-france.cfm
