Here's my confession: I own 12 pairs of Birkenstocks.  I practically live in them. They last me forever, they're comfortable, and I think they look great, especially some of the styles you get directly from Germany. Although Birks are not for everyone, for many, once they discover how comfortable Birkenstocks sandals and shoes really are, they're compelled to do what I did and spread the word to my family while buying multiple pairs.

The problem is that my Birkenstock habit can get expensive. Birkenstock shoes are not cheap. They're quality made and you definitely pay for it. But since they help prevent and treat my plantar fasciitis, the leather doesn't force my feet into an abnormal shape, they have contoured footbeds, and they last me for years, I feel it's worth it. However, I'm a sale hound. Only a few times have I bought Birkenstocks not on sale. I search out Birkenstock clearance sales and end-of-season sales, and I shop at places like Birkenstock Express, Sam's Club, and eBay to get a discount.

• Some Birkenstock retailers will offer quantity discounts, or discounts on subsequent orders placed--MJ Feet in the University District of Seattle used to do this.
• One obstacle you'll find is that Birkenstock sandals aren't treated as seasonal footwear. They're considered year-round footwear and so don't automatically go on sale when the summer ends.
• Warehouse clubs are a great place to look. They tend to stock very limited styles and sizes, but they usually have incredible discounts, sometimes as much as 50 percent.
• When you're looking online, know your the size you want ahead of time, including the widths. Often Birkenstock clearance shoes are only searchable by size and width.
• Be sure to take into account the cost of shipping the shoes when you buy discount Birks online. I usually get several pairs at once from the same vendor when possible.
• Try some of the new or uncommon styles. If you haven't already checked out eBay's selection, you may not realize that many styles sold directly in Germany, which is the home of Birkenstock, are not available at retail stores in the U.S., but only through overseas mail order. Ordering from another country isn't as scary as it sounds--I've never had a bad experience, and I've gotten some styles I thought were discontinued, like Birkenstock Phoenix and Santa Fe, two beautiful fisherman-style sandals (the Phoenix has a closed back.)
  

The Birkenstocks company uses unisex UK sizing or European sizing rather than American shoe sizes.

In the Birkenstock's Classic line--the line that has the famous Birkenstock Arizona sandals, Boston clogs and Florida sandals--a size 39 European is about a size 9 women's. Shoes in the Birkenstock Footprints line use alternate sizing, in which a size 40 is equivalent to the size 39 in the Classics or Papilio line.

Birkenstocks come in a range of widths. R is Regular, meaning wide width. N means narrow width. Medium means midway between narrow and wide.

Some lines like Footprints also have some styles that only come in a one-width option, medium width.

If you have old Birkenstock shoes that are worn in the heel and sole, while you're waiting for the perfect Birkenstock discount sale or for those snazzy Gizeh sandals to get discontinued, get your old ones repaired.

In some cases you should bring the shoes to a Birkenstock dealer for repair. In others, you can go to any shoe repair store and have heel taps put in.

If you pronate--turn your foot in--or supinate--turn your foot out--then one side of the heel may need repairing. Heel taps have extended the life of some of my Birkenstock sandals and shoes for years, particularly my favorite pair, an old Birkenstock Paris style that I don't think they sell anymore in the U.S.