Back when you were typing papers in high school you were told to write in double spaced 12 pt. Times New Roman type. Yuck. Okay, the double spacing make some sense in school since it gives the teacher ample space to write notes, but you never see it in the real world. Luckily, most people leave double spacing when they leave school, but unfortunately the same cannot be said for point size when setting type.
12 point type is not the average type size you see day to day. To be honest, it varies a bit since each font. For example, san serif fonts, like Arial, tend to be larger than serif fonts, like Times New Roman. 10 point type is a good rule of thumb for body copy size for most fonts. Of course this varies a bit based on what, and where, you're writing. It's a little hard to tell in the sample above since this is the web and typography for the web is a whole different ballgame, but it gives you and idea. You can also make the font larger for design and aesthetic reasons, but if you're just writing something standard in Word, try defaulting to 10 point rather than 12 point. It makes a big difference.