Will trains be available or do we need to reserve ahead of time!?

You should get better prices booking ahead, although you can do that after you arrive in a country. Where are you looking for prices? If it's Rail Europe they are almost always high. Try the national rail sites instead: http://www.trenitalia.com
http://www.sbb.ch/ There's info on this site about traveling by train, and you might also look at seat61.com.

Another nat. rail website, German Rail. The best, I think for schedules overall, but they only have fares for trips beginning or ending in Germany. For long distance, such as Venice to Lusanne or Lusanne to Paris, I would book in advance (but not from RailEurope). You'll probably get better fares and you'll avoid not having a seat if the train is overbooked.

Do you have a particular date and time in mind, and which exact cities are you traveling from/to?

May 22nd, Sunday. And we would like to stop some where in between Venice and Paris..

Hi Heather. Unfortunately, there is an Italian train strike scheduled until 9 PM on May 22nd. There will still be some trains running in Italy, though. You might want to contact the place where you're staying as they may be able to help you in knowing what time you could catch a train leaving Venice that day.

The trick, Heather, regardless of strike which may or may not happen as per Italian custom, is to work out where your "some where" is and then let us give you a hand. You were looking on RailEurope?

We are trying to get to Paris by the night of the 23rd because we have a hotel reserved that night. But we wanted to stop some where in between, perhaps Laussane and stay there. When can we find out about the strike and what would be a plan b? We really wanted to train through the alps. :(