Relate your assignments to your course learning goals and objectives.  For each assignment, know what you expect beforehand in terms of content, structure, level of work, length.  Base your evaluation criteria on these expected outcomes.

Clearly communicate these expectations to your students through detailed assignment guidelines, evaluation criteria, and grading rubrics.

Ask a colleague to review your assignment for clarity.

Create opportunities for student feedback before the final submission for major assignments.  This requires that students start early, allows you to clarify expectations, and can result in better outcomes.  Possible strategies include:

Ask students to turn in a self-assessment using the evaluation criteria and/or grading rubric.

Keep a record of what you liked about the assignment and what you would do differently the next time to improve students' learning outcomes.  You can also ask students for feedback on the assignment as part of your final course evaluation.

Final Thought:
Remember that designing effective assignments is an iterative process that requires reflection and a willingness to experiment with new ideas.

The types of exams you give, in terms of material included, ways of asking questions, and levels of thinking required, set the tone for the course.  If you want students to analyze, synthesize, and critically assess, your exams must reflect this.  If you ask questions which only require reiteration of facts, then that is the level at which the student will approach the course.  Equally importantly, your approach to teaching (e.g., what you concentrate on in lecture, discussion, labs, and other classroom activities) should mirror what you expect students to know for the exams.

Relate your exams to your course learning goals and objectives.  List the important concepts, principles, and skills you want students to master. Then list the various ways in which you have taught the material and fluencies you want the student achieve.

Use a variety of types of questions (e.g., multiple choice, short answer, matching, essay) that match up with the concepts, principles and skills you listed.  Provide students various ways of demonstrating their knowledge and skills.

Assess for major ideas and key concepts, not details (e.g., rather than ask for exact date of an event important, ask about the event's impact, or what precipitated it).

Manage your time so that you are not writing an exam in one sitting.  Try writing down one or two items that relate to each class session just afterwards.  When you are ready to draft your exam, examine these items, in concert with your goals for the course.

Use homework or in-class activities to give students practice at responding to items like those you will use on the exam.

Ask your TAs or a colleague to review an exam for clarity before you finalize it.

You may want to let students bring a "memory jogger" card to class, with important facts, figures, and/or equations, etc.  It means you can ask more sophisticated questions and the act of deciding what to put on the card is a great study experience for the students.

Final Thought:
Think about ways to get the students to learn what they didn't know on the exam. You might redesign or create new assignments, encourage students to come to your office hours, schedule a review session, or let students rewrite part of an exam for partial credit.