Avoid starting sentences with an -ing word. It gets monotonous, and can easily lead to horrible grammatical errors. Once in a great while it is useful, but more than once per chapter may be too much. More than once per paragraph is a very bad sign.
Try to avoid use of "as" to connect two different actions. It is not good usage, and it becomes a noticeable device. The poor little word has too many other things to do, it should not have to be a chronic substitute for "while" or "and."
Was-ing is another bad habit. Every character was (verb)ing (frequently as another character was (verb)ing). Be aware of it. Do not do it unless absolutely necessary to describe simultaneous ongoing action. Take a minute to think. There are a multitude of ways to describe anything.
Example using all three ickies:
Yanking angrily on the laces, Jack tied his shoes as Jill was filling the pail again. "We're not going to fall down that %#^&%*@# hill again," he muttered.
Obviously it works as a sentence, and is not too bad once, but go on like that over and over...
Carrying the pail between them, they started down the hill. Jack was whistling as he stumbled on a rock, jerking the pail and making Jill lose her footing. Letting go of the pail, Jill began tumbling down. Jack was reeling as the full weight of the pail of water unbalanced him. Sloshing water all over his feet, Jack was grabbing at the pail with his other hand as he tried to regain his balance. He failed, falling just as before.
"Son of a beech!" he exclaimed as he fetched up against a tree.
Mary was passing by with her lamb as Jill got up, dusting herself off. "My goodness," Mary said, "how could you two have fallen again?"
"You don't know Jack," Jill replied.