I begin the writing portion of my comprehensive exam tomorrow. I have 3 weeks to prepare 3 essays, based on what I have read for the last 5 weeks.

The kicker is I don't get the questions until tomorrow!

Are there any strategies concerning how one should approach this exercise?

the best strategy to keep in mind is simplicity.

make sure u truly understand the ROLE of each information u've digested for the last 5 weeks.

it's good to break an essay into :
1. outline
2. question
3. answer
4. justification

then formalize the answer of each question into actual writing ie paragraph and what not.

example? (i'm gonna use a really simple example here, so don't laugh)

QUESTION :
write an essay on the procedure of brushing ur teeth. explain the difficulties that may arise, as well as the appropriate measures that can be taken. finally, discuss the best alternative in term of the trade off available.

OUTLINE
1. introduction
2. background
3. process
4. difficulty
5. solution
6. best solution
7. conclusion
8. references

OUTLINE - QUESTION
3. process
steps?
rationale?

OUTLINE - QUESTION - ANSWER
3. process
steps? put toothpaste on toothbrush and sprinkle water onto it.
rationale? water can enhance the fluidity of toothpaste by reducing its viscosity.

OUTLINE - QUESTION - ANSWER - JUSTIFICATION
rationale? water can enhance the fluidity of toothpaste by reducing its viscosity.
Justin and Timberlake (2011) in their recent experimentation on toothpaste effectiveness has confirmed the probable impact of water by examining 300 men and women in their pre-sleeping repertoire.

this way, u can control ur writing and systematically check its flow and completeness.

hope it helps.