Many of the leading manufacturers today produce great products that can withstand an unbelievable amount of abuse. However, it is always helpful to clean your gear up and do the required maintenance when needed. Cleaning your fishing reel is very easy to do and will only take 5-10 minutes. These few minutes can improve the longevity of your gear tremendously though.
The first thing that I like to do is take off any line that may be on the reel and then rinse the reel in fresh water. After rinsing it off, it is best to clean the reel with a lint free rag or something similar. You really are just trying to dry off the water, but you can do a lot of cleaning by just rubbing the reel with a rag. Next is where the cleaning begins. For a spinning reel, you will need to remove the drag knob off of the top of the spool so that you can remove the spool. After removing the spool, clean any debris inside of the spool and outside of the spool with some q-tips and rubbing alcohol. There will be a small axle that the spool sets on. At the bottom of the axle is usually a ball bearing. After cleaning the area around and on the ball bearing, place some fishing reel oil on the ball bearing. Do not place more than a dot though, as too much will splatter over the reel and attract dirt. You can replace the spool onto the axle along with the drag knob after cleaning and oiling the ball bearing and inside of the spool. Next you will need to remove the fishing reel handle and place a small amount of oil on the handle axle, the ball bearing inside, and the opposite ball bearing on the other side of your reel, if your reel is outfitted with one. For a spinning reel, this is pretty much the basic maintenance that you will want to do every so often. You can take apart the actual internals of the spinning reel and apply reel grease, but this only needs to be done once in a blue moon.
Bait casting reels are very similar, except you take the spool off by removing the drag system. First thing first you need to rinse your reel off and clean it with alcohol. Next you will need to remove the spool. This will be slightly different for each reel, but you can refer to your owner's manual to look at the proper way to remove the spool. After removing the spool, oil the ball bearing closest to the internal gears of the reel that the spool shaft slides into. Oil the ball bearing that is on the drag plate as well. Lastly, you will need to oil the long shaft gear that the level wind works off of. As with the spinning reel, you can always take apart the reel to reach the inner workings to apply some grease, but this doesn't have to be done very often.
There is not much to cleaning and maintaining your reels, but it can sure make a difference in the life of your equipment. A few minutes can go along way in the aid of controlling the lifespan of your reels.