If you do not know if you suffer from Gum Disease, these are some of the following symptoms of it: deep red/purple gums, they bleed easily when you brush your teeth or poke them, and you constantly feel the need to touch them (such as sticking sharp objects like your fingernail into them). If you suffer from those two symptoms you may want to go consult your dentist as soon as you can and he will give you the appropriate antibiotics to help you rid the disease.
As with any oral disease, most of them are derived from the habit of not having a cleanly oral hygiene. Even if you have a semi-appropriate dental hygiene, you are still at risk of developing Gum disease and other diseases such as Halitosis and Gingivitis.
We always hear how to use appropriate oral care, but do we actually follow those rules? I know a majority of people who do not care for their teeth like they should, and have ended up with oral symptoms.
The most important thing that you can do is brush your teeth 3 times a day (or more if possible), use mouthwash and always make sure to floss. If you keep a good oral hygiene, you will be a lot less likely to develop any sort of disease of the mouth.