Well, this being my first blog, I didn't know how hard it would be to get back more often. I feel remiss in my endeavors to bring information to my students that is all in one place. What isn't a surprise, is all of the good and useful information already out there on the net. Two such sites are posted below.
Knit patterns often state which increase to use; and there are several. However, when using a pattern in which the method isn't stated, I have read that most will use make 1 (m1). It isn't because this gives the best result, however, but because the knitter hasn't been exposed to more appropriate methods for the desired result with a particular pattern. That is, when you're new, you tend not to get extensive information that comes with more exposure to different, more varied and/or difficult patterns that necessarily add to your "bag of knitting tricks." Frankly, the pattern writer is equally at fault by assuming the "correct" method for the job will just be known to the knitter. The second choice is knit front/back in the same stitch. I like this, but it leaves such evidence of its usage.
Since increases lean left or right, patterns should be written with the preferred method for each increase and often pair left lean and right lean for a better visual effect. The wrong increase can make your work look sloppy, not like "the picture on with pattern" and can leave you disappointed without even knowing why. Snore, yawn, I'm boring you, right? Okay. For a good list generally, see: http://www.knittinghelp.com/videos/increases and choose accordingly.
NOW LETS GET TO THAT "INVISIBLE" INCREASE. I was recently attempting to make a project that was all about the increase...and the increases I made were so blatant and obvious that I was disappointed. Wanting the increases to be as invisible as possible, searching the net, I found this tutorial: http://techknitting.blogspot.com/2007/05/very-nearly-invisible-increase.html
I must admit, it is a perfectly benign smooth increase. It doesn't seem to lean either left or right, and in usage it looks, to me, like a fork in the road, as if the stitches magically multiplied with little tell-tale sign at all. I've knitted for years now and never saw this increase anywhere. While other increase methods are equally purposeful, this is great when you want it to be as inconspicuous as possible. I don't think I'd use it for raglan shaping--there I like a little "seam" and demarcation to show what happened at the shoulders.