This. Contrary to popular belief, it is actually way harder to take notes on a computer unless the class is all powerpoint slides. You'll probably find yourself with pen and paper (which I prefer anyhow)
As a doctoral student and lecturer at universities, I've had lots of experience on both sides of the classroom, and this is what I think. It's just my opinion, of course, but hopefully it helps.
1) Don't use a computer in class.
It is distracting to the lecturer (tap-tap-tippity-tap) and the students around you. And, unless you are extremely self-disciplined, you'll end up doing stuff that will distract you (even I am guilty of that--googling names and terms mostly, but still distracting). Most importantly, it is very difficult to take notes well by just typing them out as you hear them (I've tried all sorts of programs), and for many people (like myself) the information doesn't seem to stick in the mind as well when you type.
2) Take handwritten notes.
Scan these into pdf form (inexpensive portable options include Fujitsu's scan snap), name it with the date and class name (110511macbook). When you are reviewing later that night, or the next week, or whenever, you can type them out. In general, you will be able to organize things in a more meaningful way, and through the process of reviewing and re-organizing the content, you'll remember it better. I have had amazing results with this process.
3) Bring the iPad to school.
I have thousands of books and journal articles in my computer. I put a bunch of them into the iPad so that I can read them anywhere. For my research, it has been invaluable. One of my main sources is a medieval collection of documents that is largely contained in two rare publications of about 35 volumes each. By scanning all of them (that was time consuming) I can now access everything anywhere I am, and I don't have to go overseas just to read a book. As an undergraduate, you probably won't have this issue, but your instructors will likely supply a lot of materials in pdf form.
4) Either size is probably fine.
I have a 13" Macbook Pro / 8gb RAM, and it is perfect for my needs, but I don't do any gaming, and I am in the humanities, so most of my tasks don't involve heavy computational power. The 15" is obviously better, but it is more expensive. Fortunately, it doesn't weigh a whole lot more than the 13", so I think the decision really comes down to price--how much do you want to spend?
5) Get a lock.
Kensington sells them. So many students get their computers stolen each semester. It is insane. Lock it up securely if you even leave it for a second. Even then, a thief might get it, but at least you have done what you can to reduce the danger.
6) Get insurance.
See #5.
7) Use online backup.
See #5. Also, computers breakdown all the time, especially (I have found as an instructor) in the wee hours of the morning before a paper is due. The odds of this happening to so many students at once are astronomical, of course, but what can you do
If you have the cash, pay for Sugarsync or some other service that will sync all of your files. If you don't have money for it, they offer 5GB free, so create a folder for important school stuff, sync it, and set your mind at ease.
8) Here are some apps you might want to try.
This is a little off-topic, but make sure you take a look at VoodooPad (extremely popular among graduate students at my university), Bookends, and Evernote. If you don't like VoodooPad, you may want to give DevonThink, Scrivener, or some other notetaking-friendly app a try.
GOOD LUCK IN SCHOOL!
