Commands are an integral part of a language, (at least I know they are in English and in Spanish), which means there are many ways teachers to create activities around commands that have a focus on communication and not on grammar rules.
Below is an activity that will keep the students engaged while focusing on meaning. You can tell students to write informal or formal commands. Both will work fine with the assignment.
1. Prepare for the activity by writing a list of How To topics. I've included mine for you to use or for help give you ideas.
A - How to plan a trip to Hawaii.
B - How to plass Calculus with an 'A'
C - How to impress your boyfriend/girlfriend
D - How to convince a police officer not to give you a speeding ticket
E - How to become a millionaire
F - How to earn/save money for college
G - How to lose weight
H - How to win a marathon
I - How to write a novel
J - How to throw the best party of the year
K - How to avoid/discourage telemarketers
L - How to be a great friend
M - How to make someone smile
N - How to succeed at your job interview
O - How to learn a 2nd language
2. Model the activity. Ask the students (in your TL) to name suggestion they would give to their friend to tell him/her how to get an "A" in your class.
3. Tell students to find a partner. Each group randomly chooses one of the cards A-O listed above.
4. Give the students a large sheet of paper, (I have a roll of white butcher paper that I use for activities like this), and a marker. Allow 8-10 minutes for students to write 6 commands to tell someone How To do whatever is listed on their notecard. Then students hang the papers on the walls.
5. With their partner, students write A-O on a paper. Read the lists on the papers and decide for what the commands are written. Write answers in Spanish.
6. Switch papers with another group to go over the answers.
Having groups of 2 helped to keep all students engaged. The one part of the activity that I wasn't pleased with was when we went over the answers. I felt as if I were losing some of the students' attention. I'm still trying to decide how to improve that part of the activity.
A variation of the above activity is to tell the students to write their lists on an 8 1/2 x 11" paper instead of a poster size paper. Then list the HOW TO categories on the board. Read one of the commands that the students wrote and students decide for which category the command was written.