Clean your air conditioner filters!
If you are pulling out your window units from last year and installing them into your windows, before you use the air conditioners, you must either clean the filters thoroughly or get new ones. The filters contain all kinds of pollen and dust that can wind up in your lungs and make the air conditioners far less effective.
To clean the air conditioner filter, make sure the air conditioner is off, then pull out the filter. Wash the filter in your sink with a small amount of dish soap and water. As you are washing the filter, use your hands to kind of scrape the dust off the filter. It’s most likely some kind of foam or mesh so it doesn’t just slide off without a little help. Once the dirt is completely removed, rinse until all of the soap is gone. Hang to dry.
Now go back to the air conditioner itself and wipe it down with a wet cloth. Remove as much dirt as possible. If you have a brush or a feather duster, you can dust inside the air conditioner where the filter goes. Once the filter is dry, add it back and you should be good to go!