[Jan2013] For an update and new information, see the thread on The Modern Synthetic Reed at clarinetpages.info.
Most of the time, I use Legere plastic reeds, Quebec cut (for a darker sound), and number 4 in strength. They last a long time, and are completely consistent. You can rely on them responding the same way every time. In the normal (non-Quebec style) I have enjoyed using the standard model 3 1/2 strength. But very few younger players will want to use reeds as hard as I am using.
Generally speaking, for both real cane reeds or plastic reeds: For younger players, try to get them used to at least a #3 strength reed. If you use something like a soft 2 1/2 reed, you will tend to get that thin, nanny goat clarinet sound that everyone hates, and the upper register will be flat or not respond at all. Use a reed that makes you work a bit. One that makes you blow. You'll get used to it, and the reed will become a bit softer as you “break it in.” A reed that starts a bit hard will also last longer.
[15Aug2014] I have found that the Reserve reeds by D'Addario are consistently good.
I am guessing something like this will work well. (Someone with recent teaching experience, help me!)
Legere reeds come in 1/4 increments, so try 3, 3 1/4, 3 1/2, etc.
The reason for the difference in reed recommendations is because the Fobes Debut has a 1mm tip opening, and the Hite Primiere is a bit less than half that open.
(For non-Quebec, maybe it would be best to start at 2 1/2, 2 3/4, etc.)
The Legere company has made the process of finding your perfect strength easier. They will replace the sizes you buy that you don't like. Just return the ones that are the wrong strength, and they will send you the size that suits you.
The only draw back that I find with Legere reeds is that I sometimes cannot jump a large interval to the highest notes, like jumping to the altisimo high g (four lines above the treble clef). If I am going to be playing a piece with notes higher than high g, I will go back to my cane reeds. But that seldom comes up for me when playing in church!
What reeds do I recommend for a beginning student?
Some other plastic or composite reeds may be quite good also. But Legere seems to have the most proponents. Still, those using plastic reeds are very much in the minority.
How to store reeds:
Store your reeds in LaVos plastic reed holders— the ones that come in different colors. Each one holds two reeds. These cost just a dollar or two at most music stores.