Re: How do you identify your lines?
This is a very good question. Some simple things can be very helpful. Here is a system I used in Alaska for storing fly lines.
You need a wall like in a closet or garage or where ever you store your fly lines. I had some spare spools but you can use the spool that the fly line comes on. Put nails on the wall, or a backing board, that will hold the spools in place. Also mount a shelf under your line up of spools about 18" below the bottom of the spool.
Now if you put a fly line on a reel you put a sticker on the line spool on the wall. Something like: Galvan #3, WF 5wt, SA and the date. Now you can fish that line and when ever you are not going to use it for a while or after every trip or what ever fits your needs, hang it over the spool. Pull the line off of the reel and clean it. Then coil the line in loops about 15" to 18" long. Now lay the coiled line over the spool so it hangs down and place the reel on the shelf below.
So what we have is a shelf with the fly reel setting on it. The fly line still has the backing fasten or it can be removed. The rest of the fly line is in coils being suspended over the wall spool directly above the reel. This keeps the fly line in relative large coils. You can look at the spool the line hangs on anytime you want to know what fly line it is. If you hang a different fly line on the spool you add a new sticker on the wall mounted spool. If you remove the fly line from the reel and disconnect it you can hang it and sticker the spool.
This is more of a storage system and it will keep your fly lines from getting little coils in it. You can make your shelf and backing board from nice wood and stain it. You wife will be a lot happier about that.
If you want to mark the fly line its self use the system that Mark suggested. It is important that you write down your number system so you know what it is next year or five years ahead.