Before you put any pieces down, push the button. It's the quickest way to find out which, if any, objects within the level move, and how you can utilise that movement to get to the exit. Start simple: lay down a couple of bombs or other objects and see if you can get to the exit with the minimum of fuss.
The same applies when creating a level. There's no point in overcomplicating matters on your first attempt. Besides, some of the simplest levels are the very best.
Play plenty of user levels to see what works and what doesn't. You may even be inspired - just don't produce a direct copy.