The usual suspect in this instance is AND.
For example: Jeff walked across the floor AND danced with Gina.
Physically, there is no way Jeff could both walk and dance at the same time. It seems nitpicky, because you can extrapolate that he danced with Gina AFTER walking across the room, but this is one of those writing snags that drives an editor batty. Editors want to see the sequence happening. This sentence is missing that THEN element. Grammatically, it should read
Jeff walked across the room, AND THEN danced with Gina.
Often, a writer is in such a hurry to get from one character action to another that she will mash several activities together in one compound sentence, leaving the reader to figure out exactly what happened, and in what order. At best, it's a blip on your reader's radar. At worst, they're wondering what the heck that character is trying to accomplish. Rather than confuse or frustrate your reader, it's much better to clarify a sequence of events.
One of the things I always point out to newer authors is that you are not there to hold your reader's hand while she reads your book. Your words on the page must do all the work of conveying your message and meaning. Always be clear in what you mean to say, or you run the risk of losing your reader's trust, interest, or both. Why let such a little word muddy your meaning? Un-pretzel your character by using THEN, or have each action take place in its own sentence. Happy writing!