Start by downloading the Exam Topics, from Cisco’s web site, (login required), for exam 642-627. This exam covers a very wide range, within the IPS family, including AIM, AIP, IDSM-2, and the 4200 series. It is not very likely that anyone has exposure to all of these devices, but at a minimum, a candidate would need to have hands on practice with a 4200 series IPS appliance, running the current 7.x software, and using the CLI. The primary tool for management of the IPS is Device Manager (IDM). The core of IPS v7 is mostly the same, across platforms. The CSM and MARS integration will most likely have to be book learning only, if those products aren’t readily available to you.
Plan to read, and then practice using the GUI interface of IDM to configure the IPS appliance, testing and verifying both understanding and implementation of what has been read. This would include virtual sensors, signature policies, rules, anomaly database, each parameter of a signature, event action overrides, event action filters, interface pairs, VLAN pairs, VLAN groups, event actions, summarization (both on the local signature and system wide), system wide settings, global correlation and operating system identification (just to name a few).
Leverage the Cisco Learning Network (CLN) where you can ask questions and get great answers to accelerate your learning process. CLN is a hotspot for those with a passion for Cisco learning and certification.
Schedule adequate time for study. One of the secrets of success is consistent scheduled study time. A great strategy for passing any exam can be found here.