If you are looking to organize a complex job search (with more than 100 potential employer contacts), you might also look into using contact software to automate the planning and tracking process. My personal suggestions would be Microsoft Outlook (included in most versions of Microsoft Office), which can handle large numbers of contacts with ease and efficiency. It provides an easy-to-use interface, calendaring, tasking, and the capabilities to both capture and update information about the people you are contacting. But whether you work with a hardcopy planner or software—or both (I use both my paper planner for daily event planning and Outlook for e-mail and contact management)—they are only as effective as you make them. Dedicate time to using them properly. Or use Excel to build a spreadsheet to track all of the key contact information.
Another alternative is to use a contact manager in Gmail or on your mobile. Some can interface with your desktop through the cloud to keep you in synch with all your contacts.
Even though you may use your computer and mobile, your should still always be ready with pen in hand. Pocket organizers are portable and available, if you don't have one, even post-it notes will work. You should be prepared to record each and every bit of information, no matter how minor or insignificant it may sound, as it occurs. Do not get caught in the "I'll write it down later" trap, because you will often either forget or lose the information by then.
No matter what you use—paper planner, contact software, or mobile—you need to use it consistently to be effective. Dedicate the time and energy to make it work for you. It takes time up front to be committed to the system, but it will definitely pay off over time.
Its amazing how often you will find yourself going back to a name or phone number that you recorded weeks or even months before. After your job search is complete, the information you have gathered will serve as the networking foundation for all future job searches. Capture the information and use it wisely.