Bus travel from Prague

According to Student Agency, you cannot purchase a ticket ahead of time for domestic trips from Prague. So I assume this is not a problem even on busy weekends because there are several competing bus companies. My only concern with that is that there are two bus terminals and if that would be a potential problem, and if some of the other bus companies are less comfortable, etc.

You can buy tickets in advance, though not online. If you can get down to a student agency office (such as the one down the hill from IP Pavlova metro station) you can buy one there.

You shoud definitely buy a ticket in advance (at least some 3-4 days). Student agency is the far most comfortable bus, with coffee and magazines, others are rather just a thing to take you from one point to another, athough they work as well (and in Czech the distances are usually not so far that you could not survive without magazine ;-)

When I wanted to buy a bus ticket in advance to Karlovy Vary, I had to specify the exact bus I wanted to travel on (date + time). Since I didn't know when I would be traveling, I had to buy it just before I got on the bus. However, there was no problem whatsoever.