Summarize this article:

Use a hose to wet all of the awning before you begin to clean. If you don't have a hose, you can use a bucket of water or spray bottle to do the job. Make sure the awning is still wet before you apply the cleaning solution. Fill a bucket with water. Look for a dissolvable solvent that is made for or will work on aluminum. It is best to buy a solvent that is specifically made for aluminum, because a general cleaner may be too harsh or not work. Pour the solvent into the water. The amount of solvent you use depends on the type you're using, so check the label for instructions. Submerge a brush into the cleaning solution you've created. Begin to scrub the awning. Continue to scrub until you've cleaned the entire awning. Use a garden hose and rinse off the awning. Make sure you rinse off every part that you used the cleaning solution on. A film will appear on the awning if you haven't rinsed it off properly. Rinse off any concrete or wood that the cleaning solution may have gotten on.
Hose down the awning. Mix water and solvent. Scrub the awning. Rinse off the cleaning solution.