If you don't mind spending the money, I would by both the Official Certification guide for ROUTE for test study, and the Foundation Learning guide for ROUTE for refference.
The steps that Jaris mentioned above is how I'm going about CCIP, and sense I'm already CCNP certified I have already passed ROUTE and am going through BGP right now.
I have already passed all the exams, the last and the worst was QoS, I took it the last week, so I'm CCIP but I realized that there will be a new CCNP SP certification which will replace the current CCIP.
If you have not started yet, I suggest to start the new SP path (CCNA and CCNP SP).
I have studied but I have not taken a test yet. I'm debating on whether I want to do another associate level cert or just switch to the CCNP so I can get a professional level under my belt. The CCNA SP is the perfect cert for my position cause I have to do all of that stuff at work but it's hard to judge with no exam guide.