Browse through the list of available subjects, read the course descriptions, and choose the ones that offer lectures that you’d happily attend on a regular basis.
Sometimes, you can find electives that are overlapping with your main subjects to some extent. It is useful to go for these, since they will help you understand the more difficult stuff that will inevitably be the subject of one of your exams. In addition, these are often taught by the same lecturers, and if they can remember your name from the small group of students taking the elective, that might be handy when you meet them at the big exam.
As a student, you will be mainly responsible for working out your schedule, so try to make sure you have no gaps. University lessons last 90 minutes, rather than 45, and with a 10-minute break before and after the lesson, if there is a gap in your schedule, that might mean at least 110 minutes lost from your life. If you see a nice little elective you like which fits that gap, don’t think twice, grab it. You will end up with more credits and no time lost.
Check closely the course syllabus and requirements before you sign up. Some electives let you bag up to four credits in exchange for the equivalent of a school presentation, while many others make you work harder than a mandatory course to earn just two credits.
Writing your degree dissertation is the single most difficult element of earning your diploma. Be careful and avoid having to deal with courses that are not strictly mandatory in your last year. Calculate how you are going to achieve the credits in the first two years, so that you do not need to worry about that in your final year.