Promise ring.
Of course, the lady would suggest jewelry … followed by clothing. Touche. =)
Well, I’ve read through the other responses, and I’m not digging them. Maybe he could color her a picture of a kitty or something. 
I guess the straight-forward approach of telling her how he feels and asking that they see each other exclusively is just too darn barbaric for for the 21st century. Honestly, I’ve never really been in that situation … just seemed, by actions, whether both people, were interested in keeping the relationship monogomous was obvious. I mean geez, if she’s dating other guys, that’s an obvious “No” … but if she hasn’t pursued other guys and/or accepted date (or other) offers from other men, then it would appear that she already is “his girl”.
Going steady is out-dated, or so has been reported … maybe matching belly-button rings or tatoos?
Seriously, I don’t see what else is needed other than some conversation over dinner or before watching a movie/DVD.
I told him if you are a couple, then you are just a couple, no need for announcements.
I agree with this. I don’t buy the statement that they don’t do it like that anymore … unless he means young people don’t committ to just one person, without having a “sex buddy” (or two or three or …). That seems to be how it’s done “nowadays”.
I guess I never understood the complexities of college relationships. Either you liked someone enough to just see them or you didn’t. Your actions spoke louder than any words, rings, coloring book kitties, etc (although nothing speaks louder than matching outfits … good one KEJ). Pretty simple, really. Date around, eventually find that one girl that changes the way you look at everything, date her for a while (6 months for me), get engaged, get married, have some wonderful children, actively maintain a healthy marriage, and enjoy life. Then you buy a triathlon bike, and one day after stopping by the jewelry store she comes home and asks, “Did your bike cost $1200 or $1800?” It’s magical.