A superhuman character, that is. (If you wanted to learn how to become Spiderman, you'll have to find another blog.)
Unlocking the door, Tim opened it, threw his leather jacket onto a rusty hook, grabbed a packet of chips from the cupboard, and slumped down in front of the TV.
What is the problem with this sentence? The problem is that Tim is doing all five actions (unlocking the door, opening the door, hanging up his jacket, getting food, and sitting down) at the same time. Simultaneously.
Unless he's Superman (and he isn't), this obviously won't work. He can't do all those actions at the same time; he does them one by one.
Starting your sentences with '-ing' verbs can cause these problems. (And yes, I know that their technical name is present participle, but we won't go into that now.) This is not to say that you shouldn't use '-ing' verbs, it just means that you need to be very careful when doing so, that you don't cause a simultaneousness problem. (And yes, that is a word.)
Related to this is action-reaction order. The action comes first, the reaction comes after that. Don't have your character reacting to an action before (or at the same time as) the action is occurring. Using '-ing' verbs can cause this, so even if the two actions can physically occur at the same time, be careful that one of them isn't actually a reaction to the other.
Just because these are funny, I'll post some more simultaneousness-problem examples:
Spinning round, Kate ran towards the school.
Slamming a hand over his mouth, Joe screamed a warning.
Switching on her computer, Tina opened Outlook.
And an action-reaction one:
Spinning round, Mary felt a presence behind her.
Note that because Mary should feel the presence behind her before spinning round, switching the two parts wouldn't change anything. '-ing' sentences happen simultaneously.
Feeling a presence behind her, Mary spun around.
Using sentences that start with '-ing' (or number 4's for any other IEW-ers) can vary the sentence structure, but it is important to be careful in using them, as problems can easily occur, as can be seen above.