When you are travelling on the TGV or a French regional train SNCF will give you the option of first class or second class travel.
With these names come a number of mental pictures. First class feels like you will be reclining in large seats, being served copious amounts of food and drink while smoking a large cigar while those poor people in second class will be jammed in like sardines, six across and two high.
However, this is not the case on the French train system. In fact, within France there is almost no difference between at all between First and Second class.
On the TGV, the main difference is that the chairs are slightly larger and recline slightly further (but in reality, not that far). Instead of being two seats on each side of the aisle (as there is in second class) there are two seats on one side, and one seat on the other. In first class there is very likely to be a power point at your seat. Sometimes there is a power point in second class, but not always. There is no complimentary food or beverages and no additional service provided to first class. Therefore, normally it is not worth the additional price. Although, on some occasions, it can be cheaper to buy a first class ticket than a second class ticket.
On the regional trains, there is even less of a difference. It appears mostly that first class is supposed to be quieter, and again, there may be a power point.
Therefore, if there is a price difference, it makes sense to stick with second class when travelling inside France.
This does not apply to the Thalys line which services Belgium and the Netherlands. With the Thalys service first class still has the larger seats and the power point, however the first class cars are more plushly decorated, you are provided with free wifi on board as well as a meal and beverage service. If there is only a small price difference between first and second class, splurge out and buy first class - it's worth it!
If you are looking for places to explore outside of Paris - for a day trip or maybe something longer - check out www.beyond-paris.com for ideas.