My experience pertains to on campus recruiting for full time positions. I am unsure how useful this information will be for applicants other than undergrads and campus hires. I detail my experiences in chronological order of dealing with them.
1. Career Fair
I did not interact with representatives from Procter & Gamble at our campus' career fair. It did not appear to make much of a difference.
2. Online Screening and Reasoning Test
The online screening is exhaustive, and others here at glassdoor have detailed the experience accurately. The details of the online screening process are also detailed on the P&G website, and details are readily accessible by asking your campus recruiter(s).
If you are nervous about the online reasoning test, google the Procter & Gamble Reasoning test and you should be able to track down the practice test. They will send you this link AFTER you are invited to a second round interview, but it may come in handy to look it over before you take it online. Others may disagree, but I found the reasoning test fairly easy; I remember quit a few questions around percentage increases, decreases, discounts, and the like. You can't really study for the patterns portion. No worries if you do not finish on time. I didn't finish either the online portion or the second round interview one. Word is one only needs to score a 60%, so don't stress over this part.
3. First Round Interview (Two Interviewers, one hour and 15 minutes in length)
After a resume screen and the online assessment, I was invited to a first round on campus interview. The interviews themselves are fairly long, but also straightforward. No assessment centers, group exervises, or trick questions. Chances are you will be asked questions you have heard in other interviews. You can find these questions with a simple google/bing search of "Interview questions". So don't worry about the questions, worry about your answers. They will be listening very closely.
The interviewers seem fairly interested in you as a person, and there was a lot of stress on resume content, personal history and internship experiences. My two interviewers and I spent the first 15 minutes talking about ourselves. My impression was it would have been impossible to be invited to a 2nd round without at least one great internship -- in fact, I have never been asked about my studies or for my transcript (the latter will be turned in on my first day of work). If you have a record of leadership, great experiences outside of school, and you can communicate clearly how you produced substantial results in these experiences, you're in good shape. Also be ready to comminucate how you deal with deadlines, teams, people you have had to deal with who did not agree with or get along with you, and stress your ability to get results.
4. 2nd Round Interview (Three interviewers, over two hours in length for interview; 50 Minute Reasoning Test, two meals, and two informational meetings with CMK members)
After a week of anxious fretting, I was invited to the 2nd round interview in Cincinnati. This experience is a fun one, and, depending on your schedule, includes dinner, lunnch, and or breakfast. You'll be invited to a dinner the night before your interview date, and will do lunch or breakfast the next morning with a representative from your possible department. This all depends upon your schedule, and these two meetings before the actual interview will not affect whether or not you receive an offer. Within reason, of course, as I'm sure you could totally blow the whole thing if you reveal you're a steelers fan ;). Use the lunch, dinner, and/or breakfast meetings to find out more about the job, or the interview process itself. I was told I was not competing with anyone at this point, only myself.
The on-site proctored reasoning test was longer than the online portion, and I actually found it a bit more difficult than the online portion. Still nothing to be too worried about.
The on site and final interview was just like the first, save for a few differences. The three interviewers were, of course, different from those I interviewed with on campus, and there were three interviewers instead of 2. The questions were similar if not the same as those I were asked on campus.