The first thing to consider when engaging in martial arts is your body size and ability. Although you may not have martial art abilities to start with, certain abilities, per your body structure, will either enhance or hinder your training. This is not to state that a hindrance is an impossibility to perform a task, but the difficulty level increases.
The second thing to consider, is what do you desire from martial art training. Self Defense or Fitness/Sport? Or both? Some schools emphasize both, but have more of an inclination to Fitness/Sport. Where other, very few, strongly emphasize Defense. The latter having no actual ranking system.
The third thing to consider, is not to fall into the "fad snare". Because every Jack and Jill are doing one particular, is no reason to join those ranks. Any system/school, that is fewer than the "fad", have better potential. For example a Aikido school/class, would be more interesting for defense than a Tae Kwon Do school/class. But this is not to state that one has ultimate superiority over the other.
Here's some historical data by Rhett Pilstar:
Karate is a technique of self-defense that enables self defense even when you are bare handed. This art has gained increasing popularity in recent times. Karate was developed in Okinawa, Japan. This was a kingdom located between Japan and the southern part of China. In 1607, a southern end Japanese clan Satsuma, invaded and occupied Okinawa. This resulted in great political trauma. The islanders had a similar experience earlier at the hands of their king in 1422 after a civil war. Both these instances led to the development of unarmed combat that later metamorphosed into karate.
At that time, the art offered the use of hands and legs that were trained through tough practice regime to make them able enough to face the challenges. Likewise the elbow knuckle, toes and the ridge of the foot were also trained. Japanese instructors now eliminated such an old training system due to its risk to damaging the hands. At the beginning in Okinawa the system was called 'Te'. The arts appeared to differ depending upon geographical locations and instructors. Other than that, there was the system called To-De or Tote which is alternatively pronounced as 'Karate' meaning Chinese hand.
This art was known as 'Karate Kempou' or the Chinese Hand Fist System, while it was getting more and more popular in main land Japan. In addition to karate, Japan also had a traditional institution for martial arts and this was called 'Budo'.
Ever since Okinawa was forced to become one of the provinces of Japan in 1871, there had been a political uprising by both the Japanese and the local citizens to promote the art to be recognized in the field of Budo. Hence, the practitioners started to call it Karate-Do. The Art of Karate-Do was official name during the 1930s in the mainland Japan. Among the various styles of Karate practiced on Okinawa island, Goju-Ryu is known as the earliest institute of Karate.
Some of the Karate moves include: Upper Block, Middle Block, Front Kick, Groin Kick, Elbow Strike, Palm Heel Strike, Escape from Bear Hug, Escape from Hold with Knee Strike and Ude Tanden (Arm Blocking/Toughening Exercise).