Some things I'm realizing now as I'm learning about this game and fighting games in general is:
1. Knowing what options are available to your opponent at every step of the match and how to play around them is important. This is not only needed for a great gameplan, but to also prevent yourself from getting overwhelmed with unneeded worry.
2. Defense is much more broad than some people believe. Not only does it entail blocking correctly, but also being able to tech throws, recovering at the right time, safely baiting certain things from an opponent, using the invincibility or other attributes of your attacks properly, and many little things.
3. Teching throws quickly, as much as people would like to admit they can easily, is hard to do by reaction alone. Knowing when your opponent can actually make a successful throw and learning from the habits of your opponents makes this much easier. For example, if a player has a tendency to run up to you before throwing or use it at a certain time in a combo, making a mental note of such will put you on alert the next time the situation may come up.
4. Lastly, going on with something I mentioned in the third point, it is absolutely key to be able to pick up on the tendencies of your opponent. There are many types of players out there, and almost all of them play their character differently. Being able to figure out and capitalize on the more common aspects of a person's style will often give you an advantage, regardless of the match-up.
I thought this wasn't going to be a block of text when I started...oh well.