First, don’t listen to most of what people tell you because most people don’t have a clue what they are talking about with regard to real world self protection and survival. Here’s what I can tell you:

1. Don’t get a gun, knife, or pepper spray, and think your problems are solved. Pepper spray is pretty much useless because it doesn’t incapacitate people (I know this for a fact, I’ve been sprayed and forced to fight – law enforcement training – Some people simply aren’t affected, others are too intoxicated or high on drugs, and most will still be able to fight anyway. Guns aren’t the answer either. If the person already has you in the kill box (meaning they are close to you, have a weapon already out, or the fight is on) the gun is useless. Lets not forget that most violent criminal acts are executed ambush style, which immediately places you in the kill box if you didn’t see it coming and greatly reduces your chances of surviving. Retention is also an issue. In any given year, of the total number of police officers shot in the line of duty, roughly 60% of the time it is with their own weapon. Having your gun taken and used on you is a strong possibility, even if you are trained. Same goes for a knife (to a slightly lesser extent, but can be equally as deadly). Let’s also remember that part of self defense includes taking actions that can be legally defended. Good luck if you shoot or stab an unarmed person.

2. I noticed a lot of people think boxing is a great form of self defense. Boxing is a sport, and the techniques are taught as such. Yes, you learn some good footwork and how to throw a decent punch, which definitely do help, but boxing is in no way intended to protect you in real life. I can also point out faults with every other style suggested; however, each style can contribute to your benefit as well so they cannot be completely disregarded. The trick is finding an instructor who is capable of teaching you what works and what is practical and applicable in the real world.

If you really want to protect yourself, find somewhere that ONLY focuses on self protection and does not treat it as an “on the side.” You will fight how you train and if you only train sparingly for real life, it won’t be there when you need it. Also, and most importantly, wherever you decide to train, make sure they are teaching you AWARENESS. That is lesson number one, and goes with every lesson after. Awareness is what really saves your life. Know the current crime trends and the tricks criminals are using. Know how to act in public and what to look for and avoid so that you don’t make yourself a desirable target for a potential attacker. Criminals look for targets they think will be easy. If you learn all this, and also add some techniques to bail yourself out of a situation, you will be fine. If your awareness is exceptional, chances are you will hopefully never even have to worry about actually fighting (but it’s good to know how, just in case).

Source: Yahoo Answers

You almost certainly do not want to go to the ground.  In this situation, you are an easy target and prey.

When fighting multiple opponents it is more about tactics then style. If you are truly concerned with fighting multiple opponents, you need to train in a style that addresses these combat situations.  This also includes training and live sparring against multiple opponents.  Some common martial arts that may address this are:

• Aiki-jitsu
• Aikido
• Japanese Jujutsu
• Krav Maga
• Wing Chun
• Reality Based Martial arts

Lastly, the worst thing you can do is actually try to stand your ground when there is a way out.  Sometimes you may need to “create” a way out and they involve actual fighting.  Some people may say “hit the biggest one and the rest will get scared”.  That is not always the case, and the biggest one might not be near you.  If you need to create an opportunity to leave, attack what you can, and get out of the situation.

What really matters  most is how confident you are in what you have been taught, not the style. Understand that there are very few styles, MMA or traditional, who’s only focus is self defense. Many of the traditional styles also work on building you as a complete person, not just a fighter. They tend to take longer to become effective in, but that is because they are designed that way.

If you want pure self defense, Krav Maga is a good option, however many of the places that train it in the states teach a very watered down version. Be careful.

The main problem with most MMA schools that teach the UFC style of fighting is that they train under a certian ruleset, and most never address thinsg such as weapons and multiple attackers. They never take into account that your opponent in self defense is not going to be wearing trunks and gloves. they will be wearing jeans, shoes, coats, etc. Sadly many traditional schools never consider this either. Why train for self defense on a padded level surface in clothing you would normally not wear?

Some schools even have training days where they wear regular street clothes, go outside and train on uneven terrain, practice fighting around obsticles, on stairs, gravel, etc. Not many schools I know of train this way though. I mention this because Krav Maga and some of the reality based fighting systems do train this way almost exclusivly, so for what you are looking for, one of them is probably your best bet. To figure out what is good or bad do a search on finding a good school using the find your school tool or find the best martial art style tool.

Source: Yahoo Answers