With that said, don't worry if you don't know exactly what you want to do as soon as you get to BYU. You have time to take classes that interest and find your passion.
BYU encourages all students to start into their major classes their first semester here. Even if you're not entirely sure what you want your major to be, some classes are pre-requisites for several majors. For example, many science and engineering majors require CHEM 105 and MATH 112. If you start as a biology major then decide that's not your thing and switch to neuroscience, both of those classes will transfer over to the new major. Those classes also count towards your GE requirements. Many classes will double for your GE's and major, so check out the Overlaps chart for more information about your specific major.
You can also find a complete list of classes you can take for each GE requirement here.
Even if you end up taking classes that don't count towards a GE or your major, don't worry about it! There is no such thing as useless knowledge. You want to worry about graduating on-time, but don't sweat it if you end up taking elective classes to try and figure out what is best for you.
There are also these super awesome things called MAPs. These MAPs will map out (ha, dumb pun) exactly which classes you need to take for your major and when. For example, as a pre-communications student, I should have taken Comms 101 and Writing 150 my first Fall semester. If I had known about the major MAP sooner, I probably would have! The MAP gives you a guideline to follow to graduate in four years. It also tells you how many credit hours you will need to take each semester to get the 120 credits to graduate. Some majors require more credits per semester, so it all depends.
Here is the major MAP for a BA in Communications: Journalism Emphasis. This is my major (and the best major).
To find your major MAP, log on to byu.edu. If you click on the "Future Students" tab on the home page, a drop down list will appear. From there, pick the Major/Minor list. That will list all the possible majors to choose from. If you click on one it will take you to the program requirements. Right next to where it says program requirements it will say "View MAP." There you will find a page that looks shockingly similar to the one above. If you have questions or confusion, call the advisement office that is listed on the bottom of the page. If you're going into communications, you can ask me questions as well :)
Do you have questions? Confused about how to pick a major? Curious how I picked my major? Ask me in the comment section!