Making crochet hats....I never fit the patterns?

Every time I try to make a plain ole stocking hat kind of crochet hat, if I follow the patterns, it just doesn't work out. This pattern says that the first several rounds are supposed to make a flat circle, but all of mine end up this weird wavy shape. If I fold up the excess I can change it to a flat round shape, so I'm assuming I'm making something too big.

And I'm not talking this specific pattern only, I'm talking every hat pattern I've ever tried that is this same basic idea - make a circle, make it bigger.

So how do I fix it? Switch hooks maybe? I've been kinda trying on the hat after every round and randomly adding increases and/or decreases, but it sure would be nice to know what I do wrong so I can just follow the directions!

Any advice??

http://mkcarroll.com/2007/12/basic-crochet-beanie-...

With color A, chain 4 and join into a ring with a slip stitch.

Round 1) 8 hdc into ring (8 sts)

Round 2) 2 hdc in ea st (16 sts)

Round 3) 2 hdc in first st, *hdc in next st, 2 hdc in following st* (24 sts)

Round 4) 2 hdc in first st, *hdc in next 2 sts, 2 hdc in following st (32 sts)

Round 5) 2 hdc in first st, *hdc in next 3 sts, 2 hdc in following st (40 sts)

change to color B

Round 6) 2 hdc in first st, *hdc in next 4 sts, 2 hdc in following st (48 sts)

change to color A

Round 7) 2 hdc in first st, *hdc in next 5 sts, 2 hdc in following st (56 sts)

Round 8) 2 hdc in first st, *hdc in next 6 sts, 2 hdc in following st (64 sts)

Round 9-11) hdc in ea st (64 sts)

change to color B

Round 12) hdc in ea st (64 sts)

change to color A

Rounds 13 - 17) hdc in ea st (64 sts)

change to color B

Round 18) hdc in ea st (64 sts)