A literature review IS an overview of published writings on a specific topic that helps you:
A literature review is NOT:
Have a plan and be methodical:
Read selectively, but do pay special attention to the
Abstract
Introduction / Review of Literature / Background
Methodology
Findings / Results
Conclusions / Discussion Implications
Select articles that are relevant to your topic
Critique the research with your thesis in mind, paying attention to methodology and areas for further research
Cite using the appropriate style for your discipline--even if you do not have a formal literature review as part of your poster, you should still include a list of references; think about using a Citation Management Tool to keep track of your research
Different disciplines, different types of literature reviews, but the same basic process.