While browsing through my news feed I recently came across an article by Rich Finelli on the Sass ampersand covering neat techniques to using the Sass ampersand. I would recommend reading if you use Sass in development

Among the examples given these are my favorite

Overriding styles

To overide styles on a selector you can add a parent selector with a suffix &

See the Pen Sass ampersand: Add specificity by Ezekiel (@talentedunicorn) on CodePen.

Adding modifiers to selectors

To add a selector .class-modified you can nest the &-modifier inside .class

See the Pen Sass ampersand: Adding modifier by Ezekiel (@talentedunicorn) on CodePen.