1.The duel didn't start suddenly, the character had time to look around the place taking notice of all possibly useful objects
Best for a coherent fight scene, IMO <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
2.The duel started suddenly and the character doesn't know the room well - he/she starts glancing in every way during combat and manages to see the chair.
Glance = death. Having him fall over it works better <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
3. The duel started suddenly in a place which the character is familiar with. Now, I can't have him/her thinking about the room for too long, there's no time for that during combat, and since he/she knows the room well glances are also a waste of time and make no sense. Flashbacks are out of question too.
This one is a definite pain. The best case is to have another character comment on anything that will be relevant prior to the fight scene. That way it will not take the reader by surprise.
a) I make the hero "interact" with the chair before using it to whack the rival on the head but unfortunately it still looks like plot convenience (just a different kind of it)
Depends on if they talk before they fight, or if there is some way to otherwise make it look right. Two seated characters in a room are presumably on chairs. A character deliberately making sure there is furntiture between him and someone he is suspicious of also does not appear suspect. The key is valid reason <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
In writing,
everything is a plot contivance. The trick is making it look as if it isn't. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
b) I make someone enter the room and describe it before there will be any dueling. It's a tricky one. The reader might actually forget that there ever was a description of that room and the chair will come out of the blue for him/her anyway, or some attention may be drawn to that location or even object (the author doesn't make unimportant descriptions so this room has to be special) and personally I don't want that - the duel and the "whack on the head with a chair" is still intended to surprise the reader.
If you want no prior descriptions, make sure your fight takes place in a room that would normally contain such a chair, or slip in a random compliment, like a character asking where your protagonist buys his chairs as he needs new chairs himself.
Point 3 also applies in a situation when the hero doesn't know the place but he doesn't have time to look around either - he's too busy avoiding or blocking blows.
Frantic fight scenes are never ruined by characters falling over things <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> You get a lot of good near misses and desperate side rolling that way <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
