Make sure that you checking underneath the leaves of the plants.  You want to make sure that nothing is hiding under there so that you are not missing insects.  You will find that if you leave these pests on your houseplants they can terrorize them until they are no longer able to survive. You can clean your houseplants with a soapy water solution.  This is going to be safe for the plants so that you are not putting harsh chemicals on them.  You can do this once a month to ensure that the plants are clean and free from dust and mites.  Do not over wet the plants because you may cause them to rot. You want to be careful and may even want to dry the leaves when you are finished cleaning them.

Make sure all the roots are healthy and check their color.  If they are a whitish color, then chances are they are fine.  You do not want to see brown or mushy roots on your plants.  This would only mean that the plants are in danger of becoming sickly.  You want to make sure that your plants are looking healthy and if you notice anything, you may want to change your watering or feeding habits. Take off any yellow or brown leaves that are on the houseplants. These leaves only mean that the plants are in danger of becoming sick and you do not want to leave them on.  You want to remove them so that they are not draining the rest of the plants life out of it.