Ideally, undergraduate research opportunities are coordinated and disseminated to students by the department. This makes it easier for students to find research opportunities and is more likely to attract students who might not know how to seek out opportunities on their own. A departmental information session or a website listing all of the research opportunities is generally more effective than each faculty member operating independently.
Your own courses can be useful for recruiting undergraduate research assistants. Identify and contact students who are doing well in your classes or who exhibit enthusiasm and motivation. It can also be helpful to ask colleagues, undergraduate advising staff, and TAs about prospective undergraduate research assistants.