Take the reel off of the rod. Do not leave the reels attached to rods for long periods.
Lightly rinse your reels with freshwater.
If you are using a lever drag type reel make sure the drag is on full when doing this.
Do not fully submerge the reels in water.
Do not heavily spray the reel. This can force small particles into the reel workings.
Use warm soapy water and a rag to rub down the reel. This will get the rest of the salt plus other dirt like bait off of the reel.
Spray the reel with WD40 or some such. This will force out any water/dirt that may have gotten into the reel.
Specifically spray the the handle, the drag knob or lever, the freespool button and any moving part on the reel such as the line alarm.
Spray the reel seat on the reel.
If the reel seat on the rod is metal, spray that also.
After spraying, work any moveable parts to help get the WD40 in and around them.
Try not to get too much of the WD40 on the line. But do not be too concerned as it will not put the fish off the bite.
Let the reel sit for an hour or so with the spray still on. Then wipe the excess off with a dry cloth.
For lever drag and star drag reels - leave the drag in freespool and turn the line alarm on to provide some tension on the spool.
For front and rear drag spinning reels back the drag right off.
The idea is to not leave the drag compressed in one position for too long. This can wear out the springs etc inside the reel.
Store the reel in a cool dry space. Do not leave in direct sunlight as the UV light can make the line perish.
After extended heavy use or every year or so have your reels serviced by a qualified service agent for your brand of reel.
1- At the end of each season, I take all the reels off of their appropriate rods.
2- Completely breackdown and degrease every reel
3- Build up and factory lube each reel
4- Store them in a water tight gun locker
5- I put my rods through the shower in hot water and wipe them off.