You have the sofa. You have the chairs, the TV, the lamps. The last big piece for your living/family room is likely to be the coffee table.

Yikes.

Finding a coffee table you like that also fits into the room and your game plan for the room can be quite the challenge. You think you'll know it when you see it. But how do you know which size, height and shape will be right without looking at dozens?

We turned to interior designer Mitchell Putlack for some clues.

Know thyself. Consider how you're going to sit at the coffee table, Putlack says.

"Are you going to sit on a sofa or chair and put your feet up on the table?" If so, look for a soft, ottoman-style coffee table and put one or more trays atop it to hold food and drinks. And make sure the table is at seat height, so your legs and feet are comfy.

"Are you going to sit on the floor and eat off the coffee table?" If so, look for one that you can slide your legs and feet under. Solid tables and those with lower shelves won't work.

"Are you going to sit on the sofa or lounge chair and eat from the coffee table?" If so, look for one that's "a little higher than your average coffee table," Putlack says. Average height is 18 or 19 inches.

The 18-inch rule.

Putlack recommends placing the coffee table 18 inches from the sofa or chairs - in almost all instances. "Anything more puts the table too far from the people sitting on the sofa," he says.

Knowing this rule can help determine the table's shape.

A small, round table could be perfect for a small space, Putlack says. "The relationship between the edge of the sofa and the edge of a round table exists at only one point," and then it immediately starts to get farther and farther away. So you could break the 18-inch rule and pull the table as close as 12 inches to the sofa.

A square table "becomes appropriate when you have a sofa and a couple of chairs on each side [of the sofa] or when you've got a sectional sofa" with both sections being the same length. The square shape could give you an 18-inch distance to all seating pieces.

Two's company.

Sometimes, two smaller tables work better than one - for instance, if you have a "narrow space and a really long sofa," says Putlack, who used this arrangement recently for a client with a long sofa bed. The two tables can be reconfigured as night tables when the bed is extended.

The long and the short and the width of it.

The coffee table should always be long enough for everyone seated on the sofa to be able to reach it without getting up, Putlack says. "But it should never be as long as the seating area of the sofa." You want people to be able to move away from the sofa.

Depth also matters - but it varies enormously depending on the size of the room and the placement of furniture adjacent to the sofa (the orientation, number and dimensions of the chairs). Refer to the 18-inch rule.

But keep this tip in mind: "If you want to make the adjacent seating spread out, but you don't want the coffee table to be excessive in size, place an occasional table between the chairs" and forgo the rule, Putlack says. That way, everyone has access to a flat surface.

The fret factor.

Consider "who's going to be using the table and what they're going to be using it for," Putlack says.

If it's kids with crayons or homework or adults without coasters, choose a hard material such as a stone or laminate. Or choose one that's "already got imperfections," such as a distressed wood table, so additional flaws simply become part of the patina.