Rinsing Your Gear in Fresh Water
You heard it from your instructor (hopefully!) and you've heard it from virtually every dive shop - wash your gear in fresh water after diving!  Everybody does it ... but do they do it right?  Here's some advice on giving your gear the fresh water rinse it deserves.
Warm fresh water is better than cold
But anything fresh and clean will do fine!  If you have the luxury of being able to take your gear home and rinse it in your bathtub this is your best choice!  Use a hose outside for a quick initial rinse before taking your gear into the bathroom.  Then fill your tub with some warm (not hot!) water and gently place your gear, except for neoprene items, in for a 5 minute soak.
Slosh things around a bit to dissolve and dislodge salt and sand particles and then remove them from the rinse.  When all you have left is the wetsuit, boots, gloves and other neoprene items, add a bit of wet suit cleaner to the water and throw them in.  Slosh the stuff around good and then let it soak for about 5 minutes. Drain the tub and rinse with clean water from either the spigot, or shower attachment.  The warm water is better at removing salt deposits and the suit cleaner helps to remove those "special body odors."
ALWAYS REMEMBER !!!
Make sure the dust cap is securely in place on the first stage of your regulator and that you never depress the purge button while washing your regulator.
Be careful with the regulator!
Remember that while the regulator is designed to function underwater it is not designed to be filled with water.  Check the dust cap again to make sure its securely in place on the first stage.  You don't have to grind the yoke screw through it, just make sure its snug!  Next, if you have hose protectors on the hoses it is a good idea to pull them back slightly and rinse underneath.  This is an area most people forget, and one of the first where corrosion takes hold unnoticed!
Some people use colored hose wrap for cosmetic and protective reasons on regulator hoses.  These wraps are a great way to protect hoses from damage and abrasions, but failing to clean under the wrapping can lead to even worse damage.  While you rinse slide the wrapping back and forth gently to flush water underneath and dislodge any grit, sand, or salt crystals from underneath.  About every six months or so it is a good idea to remove the wrap completely and give the hoses a good cleaning and visual inspection.
To purge or not to purge?
While the purge button works very well while the regulator is connected to a tank, allowing air to flow downstream into the second stage and into your lungs, the reverse is a bad thing!  Pushing the purge button on a second stage while washing the regulator will allow water to flow UPSTREAM and into the hoses and the part of the first stage that is supposed to remain DRY!
WARNING:
Flooding a regulator and NOT having it serviced immediately can cause the regulator to fail and free flow without warning!  This is a dangerous situation!
It is highly recommend that after washing the regulator you attach it to a scuba tank and THEN purge the second stages to dry the valve mechanisms and second stage internal housings.  How can you tell if water has entered the 1st stage?  Remove the dust cap and look at the filter in the yoke orifice.  If there is any green discoloration on it you should have your regulator serviced.  If there is any other color present other then silver I recommend having the tanks you use visually inspected for rust or corrosion.
Don't forget the INSIDE of your BCD!
When you let all the air out of your BCD on a dive some water will get inside - guaranteed!  The more that accumulates inside the bladder the worse things will get.  Your BCD is nothing more than a large heavy-duty inner tube and the worst thing is for the inside to get dirty.  When the salt water dries inside it leaves crystals, that can have sharp edges and grind through the material. Just as bad is the mold that can take hold!  When you rinse your gear it is important to remember the inside of the BCD.  Press the oral inflator button while holding a hose (or faucet head) against the mouthpiece.  Add a liter or two of fresh warm water to the inside of the BCD.
If you have a BCD wash solution (available in most dive stores) add the recommended amount before adding the water.  Slosh the water around inside and drain.  Repeat at least once, and more if you used a cleaner solution.  After you've drained as much of the water as possible inflate the BCD at least halfway and hang on a BCD hanger to dry (out of the sun please!).  If its going to be awhile before you use the BCD again it is highly recommend inflating it with air from a scuba tank several times over several days.  Tank air, being 99.9% humidity free will help dry the bladder inside and prevent mold formation.
Lube that Dive Knife!
Here's a fact of life:  Stainless Steel isn't Stainless!  Even the best will rust if you don't take care of it.  When you first buy the knife it is a good idea to take it apart and apply a hefty coating of silicone grease to all metal parts.  Afterwards I recommend applying a thick coating of silicone any time its needed.  The silicone grease keeps saltwater from contacting the blade and thereby protects it from rust taking hold.  Now you may not want to use the knife for cutting your lunch apple without wiping it off first, but it'll last years and still shine if you keep it well lubed up!  Take the time to do a little knife maintenance every time you wash your gear and it will keep a sharp edge and be ready when you need it!
Don't Forget to Rinse The Tanks!
While they are made of painted steel or aluminum you should take a minute to rinse the tanks with some fresh water.  Salt and sand can build up in the valve knob and orifice, o-rings can degrade and crack, and pitting can damage tank surfaces under those black plastic boots.  Since you're rinsing everything else it just makes sense to spray the tanks down too - the guy who has to fill them will appreciate it!
Neoprene - Don't fold it! Roll it!
Packing a suit away for the winter or getting ready for a vacation?  Neoprene has a nasty habit of remembering folds and some may never recover!  If you can't hang a suit all the time it is recommended that you lay it out flat and then roll from the legs upward.  Remember!  Roll, don't just make short folds!  When you get to the top just roll the arms inward so they cross each other.  While hanging is still the best, rolling is well-suited for travel or short term storage.
Things that are BAD for your gear!
Freezing!
Here in the Northeast this is a real issue to deal with.  If you store something wet and it freezes permanent damage may result!  Seams can fail, rubber can crack, ice can cut, etc.  Make sure all your gear is dry if you have to store it in a cold storage room or other unheated area.
Sunshine Isn't Healthy ... for Your Gear!
Believe it or not leaving your gear laying around in the bright and hot sunshine for long periods of time is bad and will lead to drying, rotting, cracking, and fading of various parts of your gear.  Neoprene rubber is affected by ultraviolet light and wetsuits, boots, hoods, gloves etc should not be left hanging in the sun any longer than necessary.
Even better, find a spot in the shade to hang your gear to dry, it may take longer but your gear will last longer!  BCD bladders, Low-Pressure Inflator Hoses, and Regulator components are also affected by prolonged exposure to sunlight.  Once your gear is rinsed, of after it has dried, pack it away and move it into the shade.
Wet Storage.
Okay, having wet gear in the trunk of your car for the drive home won't hurt, but leaving it in there for a week may cause your dive buddy (and even you) to hold your nose the next time you open the gear bag!  This problem is compounded if you're one of those divers who frequently relieves himself (or herself) in the suit (while diving).