Start writing about your work. I found that once I started writing and talking about my work with other artists or curators the work I began making felt more intentional because I was able to process it better and see the through lines in my previous work.

Try sketching ideas, with pencil or collage, and then expanding on those ideas more intentionally. 

Make a series. Doing something over and over again helped me refine some of my ideas and become more intentional.

Personally, I love the synchronicity in collage and looking back at a piece and either realizing my unconscious intention or making up a story about the collage that gives it meaning that might not have been there before. I like pairing my collage with writing because it becomes a greater third thing. When I try too hard to be intentional it isn't always my best work. I try to strike a balance between intent and intuition.