When choosing a martial art, it is advisable for you to get to know more about it before you start training. Read more about the history, philosophy, and development of combative art. You should watch some of the free video clips available out there. By doing so you will get to know what to expect during training.
After getting to know more about the art, ask yourself this question, "is that the best martial art that I really want?" You can also get detailed information about martial arts training by navigating to this website.
Sit in and observe during some of the classes or training. What about the training? Is the training too vigorous for you? Get the permission of the instructor to attend a few classes or training before committing yourself. Most of the time, you will get a few sessions of free classes or training. This will give you a "feel" of how is the art like.
If you love combative sports, street fighting, "no-hold-barred" then Mixed Martial Arts (MMA) may be what you are looking for. If the striking form of combative art is appealing to you, then you may want to explore Taekwondo, Karate, or Muay Thai.
There are many combative arts that emphasize grappling and restraining techniques. If this is what you are looking for then consider the Japanese martial art of Jujitsu, Judo, Brazilian Jiujitsu, and Sambo. There are combative arts that allow a weaker fighter to defense against a larger and even stronger opponent.