I'm learning this fishing thing by myself kind of, so some of the seemingly obvious things, I am ignorant too.  How do I know how much line to put on my reels?  I have a spinning and a BC.  The Spinning real, I usually fill right up, and the same with my BC, but maybe that's to much?  With the Spinning, I obviously know if I've put to much on the spool, but not with the BC, unless I just hav'nt done that yet.

Also, I just read a post about backing.  How can you tell how many yards you have on your reel?  My BC says it holds 120 yards at 12 lbs, but how on earth do I know if I have 120 yards on there? 

Thanks for the help guys...The only stupid question is the one you don't ask!

Fill your spinning reel to with-in 1/8 inch of the spool edge.

I spool about 1/8" from top when fully loaded, it will provide the optimum leverage for casting and for initial drag.

I usually fill the spool about 40-60% with mono backing. Some may prefer not to feel it, but I want to be able to just barely begin feeling the bump on the spool from the knot after I've thrown my longest cast and stripped off 10 more yards. This way I conserve a little so I can respool frequently without breaking the bank. It takes a little trial and error with each reel, but once the backing length is figured out, it stays on the reels for a long time.

On my baitcast and spinning reels, I fill the spools halfway with any old mono, then attach the good stuff with a blood knot and fill the spool within 1/8"

There's no sense filling entire spools with good line as you will never get down that far during the course of normal bass fishing. A mono backing (or tape) is a must with braid, or it will spin on the spool.

  Store your line in a ziplock bag out of the light and it will last a very long time.

I use backing on my reels in an amount such that 50-60 yards of good line can be added to it. After a while you get a feel for how much.

As far as knowing how much line you have on--you can get a very rough approximation by knowing how many inches your reel takes in per turn of the handle, then count the turns while spooling and convert to yards.