I don't know if this applies to knitting on circulars as well, but when knitting on dpn's, I have found it helpful to knit the first stitch onto the final needle of the circle. In other words, if you are knitting with five needles, before you start knitting the first round with the fifth needle, knit the very first stitch of the round with the fourth needle and leave it on the fourth needle as you continue knitting. This means there will be one more stitch on that fourth needle than on the other needle, and if counting stitches is important, just make sure to put a stitch marker there before knitting that very first stitch. This has given me surprisingly smooth and strong joins.
Sorry for the long post, good Lord!