How much protein should I eat?

In nutrition/RD/medical land, there is a protein rule of thumb: Eat 0.8 grams of protein per kilogram of body weight.  This is appropriate for the overwhelming majority of healthy adults (regardless of activity level).
(The majority of US adults eat WAY more protein than is needed --  more protein does not equal more weight loss or more muscle mass, fyi.)

Calculation
How much do you weigh?
Divide this number by 2.2
Multiply this number by 0.8
The answer is the recommended grams of protein to be consumed per day

Example of a 150 lb person:
150 lbs / 2.2 = 68.18 kgs body weight
68.18 x 0.8 = 55 grams of protein per day recommended for a 150 lb person
Yes, it is that simple!

If you'd like some reading on this topic, here is a well-written article (by an RD) on protein intake, weight loss, and weight maintenance.