My students keep writing portfolios. I give them class time to review their portfolios and write goals for the next essay they will write. This simple form gives them a place to write goals and, on the back, provides examples of what well-written, specific goals look like.
To encourage students to write solid goals, I sometimes offer bonus points based on how well they achieve their goals. I also have my students fill out this sheet before state testing; they review the goals they set for themselves the morning of the test.