Start by flushing the toilet, take notice of how long the water tank takes to fill up again, does it seem to be a long time? If it does, it may be an indication that the toilet needs maintenance. This would also be the case if the toilet takes a long time to flush.
Another issue common with toilets is constantly running water. Many people don’t feel this is much of a problem and get used to it but, if the water is constantly running, this is not only a waste of water but over time it will be costing you money as well. If you use a private well for your water it may also cause damage to the pump. As you can see, this is not something you should ignore.
Have a thorough check of the toilet bowl. Have chips or cracks developed in the porcelain? If you do find any, you will want to have this problem fixed immediately. Were you aware that a home inspector will note a toilet as faulty if they notice this problem?
Yes, every once in a while it's good to take some time to check every toilet in the home and make sure this essential part of the home is in good working order.