A common misconception is that all self defense training is the same. This is false. You see, when it comes to self defense training, there are many different variables that need to be taken into consideration.
A typical self defense class consists of an instructor teaching a small group of students some basic grip escapes, and self defense techniques. It's a very relaxed environment, with the instructor cracking some jokes to loosen people up, and then a bit of hands on training. The students likely demonstrate on each other and try out the techniques, but everyone is extremely careful and no-one wants to offend anyone else.
So, what's the problem with all of this? This is the approach that most self defense training school take. Unfortunately, this is a far from ideal way to train if you're serious about self defense. The reason being that you're training in a very unrealistic environment. The chances are you signed up with a friend to have a bit if fun.
I'm not suggesting that you shouldn't have a good time at a self defense class, but you should be more focused on learning than having fun. You must train in a situation that is as close to real life as possible. So, that means there must be loud screaming...real anger...shoving, pushing, and heated verbal exchanges. That's a real self defense situation. If you train like that, then you will not be caught off guard when you get in a confrontation.
So, try to find a class that focuses on simulating real life situations. You don't have to go to a class that leaves you with a broken tooth and a black eye at the end of it, but you should go to one that takes you out of your comfort zone. You really want one that ends each time with some one on one simulated combat.
Once you find a program or school, I advise you to try it out for a week. Even a program that looks perfect on paper may not be the right fit for you so, if it’s not working out, then tell them politely that you're after something different and that you won't be attending again. Many people get trapped in one school simply because they become to lazy to look for a new school. Don’t fall for this trap! Never be satisfied until you have found a training program which meets your personal needs. Many people will have to go through 3, or even 5+, schools to find a good one, but it'll be worth it in the long run.
Once you find a suitable school, you must attend weekly and put in 100% effort. Lots of people begin to slack off in class after a few months. Do this and you'll be mostly wasting your time. Always work hard in your training and your efforts will pay off. The truth is that the training should be the hard part. If you train hard then defending yourself in a real life situation will be easy.