I definitely think now is the time to start the job hunt. 4-6 months is a great time to start the job search, but it is never too early to build beneficial relationships with professionals. I feel like that is the most important part. Most of the people that have graduated and gotten a job or are graduating soon and are already employed got a hold of those opportunities through their networks. In my opinion, that is why expanding your network is so important. It is part of the job search.
I also agree that it is a good idea to search for an internship. It is a great way to see if the company is a right fit for you, and for you to perfect your skills before becoming a full time employee. A lot of companies have summer internships. A good way to find one of these is just by scheduling an informational interview with a company you are interested in. An informational interview allows you to learn more about the company and for that company to learn that you are interested.
Exploring the world of recruiting and public relations notes that with five months left we should start building relationships around us. Some may argue that this is easier said than done. A lot of us are building relationships and not realizing it. By using twitter, facebook, and blogs we are all building relationships. By using these social networks effectively we can meet great people via the internet and improve those relationships at some point face to face.