When standing in the Arizona you should have apx. 1/8 to 1/4" in front of your toes before the rim. Looking at the back about half of that amount will do it. Arizona is their classic foot bed and seems the best for most PF problems.
Then you should loosen both straps so you can just get your forefinger under them. This allows your foot to work back and forth in the shoes as you walk. Sort of an all day massage. After the leather stretches you may be have to tighten them up a notch... or loosen even more for thick socks, etc.
If they are too tightly strapped then you have the tendency to want to bend at the arch - not the best birk walk which is more of a "glide" for lack of a better descriptive word. If you do all this you will most likely develop "shin splints" from the use of your front calf muscles while walking differently than before. But it does work.
Beginners Tip: Even with a good fit, some people need to start wearing birks alittle gradually. If you are one of these people, then a good start is to first use them while sitting reading/watching tv, or using your computer. Sit with good posture, feet flat on the floor, just resting in the birk sandals. Then graduate to using them like slippers around the house only. Another key for beginners when they leave the house is to remember to walk alittle more slowly in them, don't pound down and don't bend at the arch. Think about each step for a while and pretty soon it is automatic.
When I first started wearing birks, my feet were in 24 hr, constant pain...so I wasn't aware of my feet hurting because of the birks. But, I decided to keep them on 100% for 3 mths. and long before that I was seeing improvements and am now pain free if I don't stand more than 8 hours a day at work, etc. Yesterday, went Mall of America shopping and am fine today. Tired, but fine! (I have learned also, that after being on my feet for a long period of time it helps me to switch to a different pair of birks) So I keep rotating the birks I wear.