Sentence advice

How about:

"I will see you soon, my friend," Brown said. Then he left the room.

Richard

Here are my thoughts:

"I will see you soon, my friend," Brown said, and he left the room. This is fine.
"I will see you soon, my friend." Brown left the room. This is a bit abrupt but still grammatical.
"I will see you soon, my friend," he said. Brown left the room. Again works grammatically but is clunky.
"I will see you soon, my friend," he said, leaving the room. This one get's my vote. But he's walking out of the room as he says it. If that's okay, then this is okay.

Or if you want a bit of drama:

Brown said, "I will see you soon, my friend." And then he left the room.

Is this simultaneous action? Is Brown actually in the process of leaving at the same time he speaks those words? If so, your original version (Brown said as he left the room) is fine. The last of your choices (he said, leaving the room) is fine, too. Both of those, though, can only be used for true simultaneous action.

If it isn't simultaneous--if Brown speaks first, then leaves--you need one of the other forms. They all work, as do the suggestions from Seaclusion and Ziljon, although a couple of yours are a little abrupt.

I have a hunch this isn't one particular sentence you're having trouble with, but rather a sentence pattern you use repeatedly. If that's the case, the best choice is to mix it up, to use all of the variations. But be aware whether you're describing simultaneous actions or consecutive actions.

For me, as reader, and as human being, I find it unlikely that Brown spoke simultaneously with leaving the room. It seems more probably as a sequential action, he speaks first, then leaves the room. Any construction that conveys that sequence clearly, without extraneous words, would work for me.

caw

Uh... "as" actually works fine, there. I've said "goodbye" while I was walking away before. The word wouldn't stop me in that particular sentence at all.

It's when you have people speaking as they take drinks that you need to rethink sentences.

Why did you decide to get rid of that 'as'?

Nothing wrong with it there.

The use of 'as' - and other things - should be checked, but not removed en masse without thought. Remove 'as' and 'was' or whatever, if they don't work or they cloud the meaning instead of aiding clarity.

I think you want to get rid of as when it's physically impossible or unlikely to be able to do.

He said as he was drowning.

You might want to get rid of 'as' and 'was' in that example.

I think the removal of 'as' is covered in "Self-Editing for Fiction Writers".

Given that the scene is taking place inside a room, and Brown is telling his friend goodbye, the reader can probably figure out for himself that Brown is leaving the room.

Simplify.