The thing to remember here, is that Crocs are not supposed to fit like other shoes do.
Copied from crocs.com:
THE PERFECT CROCS FIT.
Crocs should not fit like other shoes:
They should fit very loosely.
The sides of your foot should not really touch the sides of the shoe.
Your toes should never make contact with the front of the shoe.
Once you have centered your foot on the foot-bed:
You should have about a 1/4 to 1/2 inch of space in front of your toes, behind your heel and when you lift the strap you should be able to comfortably get your finger between the strap and heel.
In other words the fit should be loose.
I know that this goes against everything that you have ever been used to in a shoe, but these are the parameters that the shoe was designed to be worn under.
No Pressure points Ever!
To insure that the strap is not pulling your foot into the front of the shoe, rotate the strap forward and determine if your foot rests comfortably in the foot bed and there is room all around your foot. If so, you have the proper size but the strap is too short. To alleviate this issue, work your fingers around the strap and stretch it as you go around being careful not to put excessive pressure on the rivet hole. Stretch the strap until it is just short of the back edge of the shoe. The resin material has memory and will stay at the proper length after one or two of these types of adjustments.
That last bit about adjusting the strap is where the dryer trick comes in handy. I tried and tried but couldn't get the strap to stay streched out like I needed it to be, until I tumbled them in the dryer on low heat for a few minutes, then wore them around the house for a few minutes while they were still warm. The stap adjusted itself perfectly, and it's stayed that way since. (I've done this with all 3 pairs I own.)