The simple way to avoid plagiarism is to (1) write in your own words, (2) cite and (3) paraphrase copied text. Again, make your original tables and figures. In extreme cases, put the source and indicate if you modify it or not.
Acquiring a personal plagiarism checker may also be helpful to you.
Whenever possible, do not copy and paste part of a text of someone else in your article. If you do so it must be put in quotations marks with the reference in parenthesis. Should it be an extended text you must first ask permission to the author (and in certain cases the editor of the journal).