I have found that when I first started knitting in the round with two circular needles I would drop the first needle as I moved and picked up the second needle. The weight of the first needle and the yarn on it would pull the first couple of stitches on the second needle and ladders would appear. I am not sure if I can clearly explain it but now when I move from one needle to the other I 1)pull the first and second stitch a little tighter and 2) hold the first needle up tight against the second needle, so the weight in on my finger, for the first couple of stitches. Now if anything the stitch between needles is a little tighter than the rest.
As for the ladders you can take a crochet hook or a knitting needle and spread the extra yarn out over 6 to 10. I will work the excess yarn to the right on one row, then work it left on the next row. By spreading out the extra over a number of stitches it is not as noticeable.
And as suzeeq says keep the place where the two needles meet moving around and around. I does not have to be done on every row, every couple rows.