I've made a variable to tell which animation is playing, and instead of changing the animation when keys are pressed and such, I just change it.
For the basic platform movement, I check if it's 0 then check if the character is walking, jumping, etc.
For other things, like using abilities, swimming, going up a ladder, I use other numbers.
<img src="http://i.imgur.com/F1M2XIF.jpg" border="0" />
(Sorry for the messy code, I know I could use sub-events to make it look prettier but I haven't got to cleaning it up yet)