Accurate and careful referencing of the materials you consult during your research and when writing up your work is the best way to avoid plagiarism.
Referencing involves citing the materials that you quote from or refer to in the body of your work and providing a reference list/bibliography at the end of your work.
There are a lot of different referencing styles to choose from. The preferred referencing style will vary in different institutions and even in different departments within the same institution.
If you are unsure which referencing style to use, ask your lecturer or course administrator which style they recommend.
For an introduction to some of the widely used referencing styles, go to the Referencing Styles webpage.
Whichever referencing style you decide to use, make sure that you apply this style consistently throughout your work.