Breaking-in reeds is probably the most important thing, and the thing which students most often neglect. Don't play your brand new reed for the whole rehearsal or concert- you've just killed it!
Take your new box of reeds, soak each reed (mouth or glass of water- 1 minute max) and play (5 minutes max). Do this for each reed in the box, and repeat tomorrow. Make a small mark on the reed with a pencil- so you know how many times you've played the reed. When there are 5 marks on the reed, you can start using it normally.
I used to be an advocate of reed adjustment (of course this is often necessary). I used to use the knife, and sandpaper etc. However, the tolerances of the machines manufacturing reeds have become so accurate, that it is mostly necessary for only tiny adjustments to be made. Thus, a piece of plain paper (such as from a printer/ photocopier) is really very sufficient. The paper can be laid flat on a hard surface (table or window) and the table of the reed rubbed in smooth circular motions around the paper. This is great if your reed has warped slightly, a very common occurance if the reed is allowed to dry out too much- especially in climates with very low humidity (e.g. Europe and North America in winter)- or in climates where the humidity is too high (e.g. Southern Asia, India in hot, humid times). You can also make adjustments to the reed for balancing (as you would traditionally do with a knife) by rubbing the paper (or very fine sandpaper- rubbed over itself to make it even smoother) over the edge(s) you need to adjust.
To check the balance of the reed, try to play (open C#) each corner of the mouthpiece independently. Do this by blocking off one corner with the lip while allowing the air to pass (as normal) through the other corner of the mouthpiece- then repeat for the other side. (instead of playing with your lips perpendicular to the mouthpiece- as normal- you play with face at more or less a 45º angle to the instrument)
You will feel, and hear if your reed needs balancing, which can be done as mentioned above (with paper) or by massaging the hard, resistant or "stuffy" between the thumb and forefinger- carefully.
And remember only make small adjustments at a time- and keep checking- once you've gone too far, its probably too late.
Lastly, I can't recommend the use of an airtight reed case strongly enough. If you have ever experienced practicing, or even worse- playing a concert- and the reed suddenly not doing what it could do yesterday, then you know what I am talking about- and you need a good reed case. There are many expensive good reed cases, but the most important thing is that they are kept from the perils of changing humidity. A simple "Tupperware" container is excellent because it comes in all shapes and sizes. Don't let your reed dry out completely.
The use of a "humidipak" helps moderate the humidity, also producing much less of the nasty "fluffy green" problem often associated with the old-fashioned damp sponge technique of keeping the reeds humidified.