Depending on the age group, I've actually found journaling to be one of the most effective ways for informal and ongoing writing about reading. It is easy to create journal prompts for a class novel which engage the students in personally reacting to the text (making text-to-life comparisons) but even for activities in which every student is reading a different novel, generic journal prompts are not hard to create (or find on the Internet). I have my students journal for the first 5-10 minutes of every day, and while I do not read every journal, I check them once a week and give credit for completion. If something catches my eye, I like to make comments back to my students, which often results in a personal dialogue back and forth, which many students enjoy.
The thing I like best about journals is that it does cause students to think and write, but it takes off the pressure of "formal writing" and being graded on spelling, grammar, and complete sentences. Certainly, journaling cannot be the sole source of writing in a classroom, but it helps take the pressure off of students who either do not like to write, or are nervous about not writing well.
Like anything else, reading and writing are naturally made stronger through sheer practice, and whenever I can increase student interest enough to get them to practice, I consider it a success.