Hi, I am currently planning an inter-railing trip for September with three friends. None of us have inter-railed or backpacked before and so would like any advice you can offer! As students we have quite a tight budget, plan to spend a night in Paris, then travel to Austria, Hungary and Croatia, flying back from Trieste. We have booked flights and intend on booking first and last night's accommodation - do we need to book more or just as we go along?
Does anyone know of a good, cheap hostel/hotel in Paris - I am getting very confused with the multiple conflicting reviews!!
Also any recommendations of what to do in the areas we are thinking of visiting would be appreciated - beauty spots etc!
Is it cheaper to stay in a hostel or train it overnight?
Thanks
Sarah xxx

In Hungary, Croatia and Italy a rail pass normally won't pay for. Rather cheap p2p tickets and esp. in Croatia buses are also an alternative.
The night train Paris - Vienna does exist anymore (since 10th June).
An option would be night train from Paris (Paris-Est) to Munich (München Hbf). There are special SparNight tickets, e.g. in a 6-berth couchette from EUR 39,00. Or EUR 49,00 in a 4-berth couchette (my recommendation in your case). As long as you travel before 22. September (begin of Oktoberfest in Munich) you should be able to get still this (limited) special offer. You can check availibility and book online through this site.
From Munich to Salzburg you can use the Bavaria Ticket if you use regional trains (RB, RE). EUR 27,00 for 2-5 persons.
InterRail Austria Pass
Are you younger than 26? In Austria there is a railway disount card
VORTEILScard <26 for EUR 19,90 which is valid 1 year and gives 50% discount on the normal ticket price. With 1-2 trips this card is already a good deal. You will need a photo sized like for a passport however. Not 100% sure if you can buy it as a non-resident, but couldn't find any hint into this direction in the conditions for this card.
A normal ticket (1-PLUS-Freizeitticket) for 4 persons from Salzburg to Vienna is EUR 123,50.