For each new box of reeds, I play through them looking for the great reeds, good reeds and bad reeds. There will be a few of each in an average box. I mark the really good reeds with a sharpie, set the promising reeds aside and toss the obviously bad reeds so I don't accidentally try playing one in public.
Depending on the type of reeds you play, there are different things you can do to care for and extend the life of the reed. All instrument reeds should be handled with care to prevent damage.
Cane reeds can be polished by rubbing the reed on glass to smooth and lightly even the flat side of the reed. The topside can be polished by using the smooth rounded end of another reed with long strokes down from the heart to the tip, while placed on a glass surface. This mild polishing technique will increase the life of the reed and make it more comfortable to play when smoothed out.
Plastic covered reeds cannot be worked on. They either work great or they don't. Synthetic instrument reeds can be shaved down if they are too hard and clipped if too soft.
Reed storage is also an important part of keeping reeds playing longer. I prefer a glass surface to leave the reed on when not in play. I do not agree with those that leave a reed on a mouthpiece and just put a cap on to store both the mouthpiece and reed. I always remove my reeds and place them in a reed case, cleaning the mouthpiece and wiping the reed off between uses.
There are many different styles of reed cases available today. The cheaper reed guards are fine, but there will be a tradeoff to the lower cost. Every time you have a reed jam in a little too far, or pick up a piece of something inside of it, the tip of your prized reed will be destroyed.
The most common damage to a saxophone reed happens when you are putting the sax together. When you put that ligature on, please be careful. I have split a thousand reeds in my life being careless. Some people put the ligature on and then push the reed on under it. I found this to be unsafe for the reed tip and began holding the reed in place with my thumb, while I place the ligature on over it. This works great if you have the reed tip lower than the mouthpiece tip and are holding the reed on straight.
Another problem time is when you are not playing the sax. The reed is safe in your mouth while playing, but when the tip is exposed, the brush of a hand, clothing, or somebody walking by can waste your reed in a moment. A mouthpiece cap for your saxophone is a great tool to protect your reed when it's not in the case.
Treat your reeds with care, get a good reed case and use it, and get in the habit of using your mouthpiece cap when you walk away from your sax. Some basic care in handling and storage will add to reed life and save you some money too.