Budapest-Vienna(stop 2 nights)Prague 1adult 1 senior

1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

In Sept (8th) I wish to travel from Budapest to Vienna(about 9am) , 1 adult and 1 senior,stop 2 nights then go to Prague. What is the best ticketing arrangement and where do I buy them ? I am in Australia now

In your case everything is rather simple - purchase ticket from Vienna to Prague in advance online from Austrian railways website (fares start from 29 euro) - https://ticket.oebb.at/bin/frame_ticket.pl?ticket=jticket.pl?ABBFSEL=8101865&ANBFSEL=5400201&LANG=EN
Hungarian Railways don't sell international tickets online, so you will have to purchase it at the ticket counter in Budapest. In case you'll spend couple days in Budapest before traveling to Vienna, then you'll have a chance to buy discounted 13 euro ticket. But since number or those are limited and they can be already sold out, then you'll have to pay 25 euro for the ticket or 31 euro (includes two days on Vienna City transport).

Thank you so much for your rapid response i have onefurther question .If i buy tickets from Austrian rail online how /where do I get the tickets. thanks in anticipation

If i buy tickets from Austrian rail online how /where do I get the tickets.

You just print them on your own on a regular piece of paper. It will have special bar code and all the info, so train conductor will be fully satisfied.
Will look almost the same (http://ticket.oebb.at/testticket.pdf), but with your route and your fare.

  Plus one thing I was impressed by with OBB, is that during your purchasing the tickets, you can also select which car you want to be on and your seats as well.  This was really nice...

If passengers want seat reservation (btw, it is not compulsory for Vienna-Prague trains) for the connection s/he chosen, then obviously Austrian railways will allow passengers to pick specific carriage and seat they want 

  Which I found out from my train trip from Vienna to Budapest, seat selections don't even matter.  I don't even think I sat in the right car let alone the right side of the train or anywhere near the right seat.  I don't even think my ticket even had the seat mentioned on it eventhough I selected one on the train.  It's almost a free for all and find an empty seat...

Actually yes, seat reservation on the route Vienna-Budapest is not compulsory, thus most of the passengers ignore it, there is no point to pay extra? But on some occasions (peak season, Friday evening/Monday morning etc.) train might be busy, so some prefer to have seat reserved for them.