Just a quick post.
1. Don’t mash.
— ironic with our site name I know but you won’t get better flailing about. You wouldn’t mash in a game like Super Mario Brothers would you? You should play fighting games like you would play a platformer at first.
2. Learn your normals.
Every time you play a new fighting game this should become a habit. You want to know what button does what and the range and speed of those attacks. It will help stop the mashing. For example, if you knew that Ryu’s crouching medium kick is really good when the opponent is at tip of his foot range and crouching hard punch can be used as an anti air, why would you mash? Those tools are enough to keep anyone from mashing.
3. Learn your special moves
You want to know your special moves and how they are preformed. They are tools just like normals. Go into training mode and practice doing any move that gives you trouble. Try doing it 10 times in a row without a mistake. Then 100. You what to know you character’s special/super/ultra/etc moves so that there isn’t a surprise when and if they come out by accident.