It really depends on the company interviewing.
We tend to set a small lab up and 'break' things to see if they can be fixed. If you have just completed your CCNP I'm sure the knowledge will be fresh enough that you can answer any questions thrown at you .
It is all about the job description not necessarily "ccnp". The company wants this candidate to have so and so skills as detailed in the job posting. So, ask yourself if you possess those skills sets, do you have a basic knowledge of the position? stuff like that. My first interview as CCNA was different and interesting: I was asked questions that covered CCNA 1& 2 textbook and CCNA 3 & 4 text (2007). Then, got presented with a scenario to identify a routing loop with possible solution. Almost 30questions verbally asked with the speed of light. This is no exaggeration. It was my first opportunity after passing CCNA like 2 months back. I wasn't also sure what networking interview will be like until that day with an ISP (2007). Yours might be different....I did get the job though!
I think that the usual questions might include foundation topics. Some will ask how you can resolve issues that probably are happening to them, such as loops, redistribution or some sort of recurrent problem they might have. This of course would vary by employer. My suggestion to you is to review the foundations topics of the routing protocols at the level you are. Spanning Tree, even do many companies are stacking their access layer, many others still rely on STP for their LAN redundany. As for an ISP even do you are a CCNP be proficient with BGP and OSPF and learn MPLS.
the best way for you to prepear is to have experience/knowledge in networking; everything about routing, everything about switching (at your certification level), tcp/ip, subnetting, route aggregation, port numbers and their functions, OSI model, TCP/IP model, protocols and ports assignement/funtions/applications, security, wireless, some firewalling technology knowledge like iptables, knowledge of management; sftp servers, centralized rsyslog, automatic backups, authentication, active directory, DNS, DHCP, IPv6, etc etc...the list goes on and on, but it depends on which job role you are applying and depends on which company, but you better know your stuff. dont exagerate and do not lie, because they will catch you. be honest.