How to avoid plagiarism

Tu avoid plagiarism, you must correctly cite your sources. 

Every time you insert in your paper  a sentence, a table or an image taken from someone else's research, you must specify where you've found it and you must cite the author and the publication.

Correctly citing sources improves the quality of your work, not only because it helps avoide accusations of plagiarism, but also because it shows that a thorough research has been conducted and it lends greater credibility to the ideas presented.

Exemple:

If you write in your paper:

Keep in mind that poverty is not always obvious. One in five low-income families is headed by a parent who works full-time all year; thus, it is often difficult to tell if a family is in need.

This is plagiarism, because you've used the words of someone else without attribution, presenting them as your own.

This is the correct form:

As HB Ferguson, S Bovaird and  MP Mueller state in their paper (1):

"We should keep in mind that poverty is not always obvious. One in five low-income families is headed by a parent who works full-time all year; thus, it is often difficult to tell if a family is in need."

(1) Ferguson, H. B., Bovaird, S., & Mueller, M. P. (2007). The impact of poverty on educational outcomes for children. Paediatrics & child health, 12(8), 701-706.

Depending on your citation style, you can also  write:

We should keep in mind that poverty is not always obvious. One in five low-income families is headed by a parent who works full-time all year; thus, it is often difficult to tell if a family is in need. [Ferguson, Bovaird and Mueller, 2007] 

This is not plagiarism, because you've given the authors credit for what they have written. 

You have also demonstrated that you've read their paper and you are informed about the content.