I have to get from Barcelona to Madrid. Is the train the best way to go? Should I buy my ticket/make reservation in advance?

Also any recommendations on a place to stay in Madrid, we only have one night and want to make the most of it.

Thanks!

You better come flying to Madrid. Train is very expensive and you'll probably find offers in flights (I recommend you www.terminala.com , and the company Air Europa, most Spanair flights are delayed and Iberia arrives at T4 in Barajas and a taxi costs between 10 and 15 euros more than coming from T2). And the flight is faster than the train.

I know Hostal Tokio, near Gran Via. It's cheap, clean, and comfortable.