Q.Aerate Soil
How do you aerate soil for houseplants?

Certified GKH Gardening Expert
The best way would be to make sure that the soil does not get compacted in the first place. Always use a soilless potting mix when potting up house plants. But, if you do have a house plant that needs to be aerated, you can use a chopstick or wooden skewer and simply push them repeatedly into the soil to help open the soil around the roots up a bit.

With proper maintenance of your plants, 'aeration of the soil' shouldn't be a task within itself.
Think of it as pound cake vs. angel food cake. If the soil is compacted, like a pound cake, the roots have a hard time spreading through out the container and can inhibit growth. Angel food cake has little of pockets of air that make it light and fluffy, so the roots can roam freely.
A natural means of aerating soil is earthworms. They crawl all around and make little tunnels so the plants root system can breathe.
Pre-packaged potting soil is composed of several ingredients, such as perlite, peat or vermiculite that will provide the plant with adequate drainage and proper aeration.
Every year, whether you repot a plant or not, your plants should be topped off with some organic material. A year's worth of watering will leach out most of the nutrients and pack down the soil.
I hope this explains your question...
We all could use a little lift or 'fluffing up' now and then, right? :)