A student learning outcome is a sentence that indicates what students should represent, demonstrate or reproduce as a result of what they learn.  (from Peggy Maki).  SLOs shift us from "what am I going to teach?" to "what should students learn or be able to do?"

In other words, design the instruction session around the students and the skills you (or their professor) want them to learn.

Good SLOs describe actions or behaviors and are observable, measureable, and results-oriented, which paves the way for better assessment of student learning.  They also can refer to cognitive, physical, or affective skills - i.e., students can know the function of a dictionary, where to find it and how to use it, and then feel confidence in their ability to find the book and recognize the value of the skill itself.

There's more than one way to write good student learning outcomes.  What's most important is that they are specific, action-oriented, measurable, and therefore assessable.

One formula for writing SLOs:

[Participants] "will be able to" + verb + action phrase + "in order to" + why? 

The more descriptive the phrase, the more specific the student learning outcome, and the more measurable it is.

Bloom's Taxonomy is a classification of levels of intellectual behavior important in learning.  It can be helpful in writing SLOs to use
verbs associated with these levels.

Example Student Learning Outcomes

Students will be able to choose appropriate databases in order to search for scholarly articles on their topics.

Students will be able to distinguish between primary and secondary sources in order to use those most appropriate for their assignment. 

Students will be able to construct a keyword search statement in order to find relevant information.

Verbs to avoid:
Verbs like appreciate, know about, understand, become familiar with, are vague and not observable

There are other ways to write SLOs as well, for instance, the ABCD method.  

More about writing SLOs
U of IL Tips on Writing Student Learning Outcomes