The idea of changing majors can be a daunting one. After all, it takes so much thought and effort to just declare a major in the first place; changing must be a serious pain in the brain, right?
In short: Nope! Changing majors doesn't have to be as difficult as one might think at first. Of course, there can be some extra work involved in terms of taking a few additional or unexpected classes, but the logistics of switching are pretty easily managed -- if you know what to do in advance.
Step 1: Talk to your academic adviser as soon as possible. Whether you're 100% certain you want to change your major or if you're just starting to think about doing so, talk to your adviser as soon as you can. He or she will not only need to approve your switch (i.e., sign all your forms) but also will walk you through the process. Plan for a bit of a conversation, too; most advisers won't just let you walk in and say you want to change majors without asking a few questions first. Your adviser, too, will likely review your schedule in terms of what classes you'll need to take and when. Lastly, if you're switching to another department, you'll probably need another adviser. Ask your current adviser who they'd recommend if you don't have someone in mind already.
Step 2: Check with the registrar for important dates. You usually can change your major at any time, but there will be some dates to be aware of. For example, if you need or want to add or drop any classes for this or next semester, you'll need to know by when you have to do so. Additionally, if you're changing departments, the registrar's office will need to know as soon as possible. Stop in or call to see what upcoming deadlines you need to be aware of.
Step 3: Review what classes you've already taken. If you're switching to a similar major -- say, from anthropology to sociology -- there might be some crossover with the required classes for each major. If you're making a drastic switch, though -- say, from English to chemistry -- there might not be a single crossover. Get a copy of your transcript so you can see what you've already taken. What classes can you apply to your new major? What can you use for things like gen. ed., labs, or language requirements?
Step 4: Figure out what classes you'll still need to take. Even if you're well into your junior -- or even senior -- year, you might have to start with some of the basics with your new major. Create a list or use a template provided by your new department that lists which classes (and how many) are required. How many classes are you missing? Which ones in particular do you still need to take? Which classes are sequenced that you'll need to make sure to sign up for as soon as possible?