This has proved to be an head ache many times to me. So I am documenting the same. Hope this helps me or others in future
Click on File -> Import
Now you will see a text box labelled "Select an import source"
Type "Existing" into it
This will result in eclipse to display all options avaliable with the word "Existing" in them
Look for the category named "General" -> under which there will be an option named "Existing Projects into workspace"
Choose it and choose your project.
Your project should have a proper folder structure as desired by the eclipse. If not the project wont be imported. You may have to look for the missing files/folders and put them in place
By default when you click on File -> Import, the set of options being displayed may not necessarily be from the begining. SO try scrolling up first with in the "Import" window