Mfowl isn't far off. When casting into the wind, you have a lot of slack line before the lure even hits the water. Then you flip your bail and start reeling all that slack line in without any tension on it. That is what causes the knots and tangles. When your lure hits the water, you need to reach up, grab the line and reel in the slack with tension put on it. If you do this, you will not get anymore tangles.
If you're using a bait casting reel, you can put your thumb tightly on the spool and reel in the slack, and basically accomplish the same thing. If its really loose line, you may still need to grab the line itself to put tension on it.