if you boil down a syllabus to its most core ingredient you are left with its learning goals.
on the first day of classes, learning goals signal to students what they can and should expect to learn from your course. on the last day of classes, learning goals help students assess what they did or should have learned from your course.
although your learning goals will take up a relatively small space of real estate on your syllabus, they should take up a large chunk of your thinking. think hard about what you are trying to accomplish in your course and work even harder to articulate these goals in clear and comprehensible terms. if you have taught the course before, look back on older versions of the syllabus and assess whether or not the learning goals are still relevant. if you have not taught the course before, look at your colleagues' syllabi and think about which, if any, of the learning goals you would like to continue, replace, and extend.
try to craft learning goals that engage students who enroll in your course with significant knowledge of the topic and students who arrive with zero experience - and, perhaps, zero interest - in the topic. in general, consider including 3-5 learning goals in your syllabus.
so, for example, here are the learning goals for digital media production, a course i am teaching this fall:
once finished, add the learning goals to your syllabus, save the document, shut down your computer, and celebrate your progress.