When I went to design school, the first rule of thumb taught was to make sure you have 18″ on all sides of the coffee table to the furniture you are sitting on. Well, rules can be broken, but, it is nice not to have to squeeze into the seating area and have luxury to do so.
Here’s a picture of the traditional coffee table and how it fits so well in the space
You can also use a traditional style coffee table but have a very unconventional seating area.
If you are short on space, round may work best as there is more room to walk around the conversaton area
And if all else fails, use some small clusters to push together or spread apart