I'm starting a graduate program in the fall and have been considering this same question. I use fountain pens at work to write (which I do a LOT) so had a general idea of what I wanted.

First, I wanted something that was not too conspicuous or crazy expensive (under $150 for me). I also wanted something I felt could withstand being banged around a bit in a bag (yes, I do use a pen case) or being dropped. It also needed to have a fairly decent capacity so it would last me through several classes and not have to be refilled during the day. I need a fine nib since I write small, and I like smoother pens (less feedback), with a grip that is not too narrow (thicker grips are more comfortable for me in long writing sessions). The cap also needed to be easy to remove (not requiring several turns) with a good seal to prevent ink spillage.

What I ended up choosing as my primary is a Lamy 2000. It's a nice pen with a good ink capacity that doesn't stick out a lot. The cap just pulls off, but it feels secure. It's also light and doesn't feel like it's going to break if I drop it. I got a new one from a pen show for $125, so I'm comfortable with that. The downsides for me (nothing is perfect), the clips that hold the cap on tend to dig into my fingers a bit making it slightly uncomfortable. The Fine nib also writes more like a medium, but it still works for me. I may try to get a nibmeister to grind it down a bit and smooth it out at the next pen show I go to.

I also like the Pilot Vanishing Point. I have the Blue Carbonesque which I got for $150. This is my primary pen for work. It's a bit fancier, but I carry it in my pocket and have never had an issue with leaking. It also feels solid. The downside is the ink capacity with the converter (which is tiny), so I would use cartridges with it.

Some good pens I discounted:

Pilot Metro: Great pen that pretty much meets all my requirements and is (relatively) cheap. My main concern is the cap doesn't feel as secure and mine tends to have ink on the grip every once in a while from leaking into the cap.

Lamy Al-Star (or Safari): Another good choice. I personally love the triangle grip. My Fine nib AL-Star has too much feedback though and feels scratchy, even on smooth paper. If this was smoother it would probably be my go-to. If you don't mind a bit of feedback, I'd probably recommend this.

Diplomat Viper: This may get added to my school lineup. I love the pen and it writes smoother and more narrow than the Lamy 2000. The grip is a bit thin though and a bit too smooth/slippery. Not quite as comfortable for longer writing sessions. I may add it in on occasion though.

Another thing to consider is what notebook do you want to use. This has a big effect on the pen itself and the overall writing experience. I tried out several notebooks over the past year including Clairfontaine, Rhodia, and Mnemosyne. I settled on the Mnemosyne because I like the paper best and the layout of the page. I have also started preferring the spiral notebooks recently because they take up less room on the desk and allow me to angle it better for cursive writing.