I've noticed that quite a few people have had difficulty when starting out with Alan Dart patterns, as they are getting confused with the increasing. Many American patterns mean "Inc" to mean the same thing as "M1" (make one) but that is not the case. If you M1 in Alan's patterns, instead of increasing by KFB (Knitting the front and back of the stitch) you will end up with too many stitches.
Here is a video on how to KFB!
Happy Knitting! xxx