This is a summary of the requirements for going on exchange. Make sure to also read through section 5.5 of the Student Handbook - the Handbook is binding!

You can go...
Only in your Fourth or Fifth Semester
Students who are completing their degree in four semesters at UCR (i.e. who have 30 or more transfer credits) cannot go on exchange.
With a GPA of 3.00 or higher
If you cumulative GPA at the end of the semester before you go on exchange is lower than 3.00, the Board of Examiners may cancel your application. If you are applying while still in your first semester, a grade indication from each course instructor must be submitted with the UCR application.
Having done enough courses
If you're going in your fourth semester, you need to have done at least 10 courses in the Academic Core and your major department combined. If you're going in your fifth semester, you need to have done at least 13. This is to reduce the chance that you have trouble fulfilling your requirements when coming back.
If you are a good student
You can have no shortage of credit and you cannot be on social or academic probation.