what is the best way to put new line on a spinning reel?

It may not work 100% of the time but it has for me every time I have done it. Put the label side of the spool down on the floor and then attach line to reel spool and start winding. If you want to double check after winding for about 20 or so turns of the handle, stop winding and give the line some slack, If you get a very twisted,kinky line then you have some wrong.

Bring it into Cabela's and we'll put it for you... LOL.

Tie the line off to a stake in the yard. Put a pencil through the spool and unwind it into the grass in a straight line. Zig zag back and forth until you've reached the desired length. Snip, tie to reel. Snip the staked end and wind it up. The grass will provide enough tension to remove the twist. Of course I always do it like DLALLDER does.

This works for me. Put spool on pencil, run line thru guide next to reel and crank it on like a baitcast reel. Seems to work.

Put the spool on the ground and make sure the line comes off the spool counter clockwise.

Its pretty simple, really. Look to see which way the line is going onto the reel. All that I know of go counter clockwise (as you are holding it normally, pointing the face away from you).
When you put the line spool on the ground, the line should be coming off of the spool the same way. So, as was said earlier, it should be coming off counter-clockwise as well. This will minimize line twist. For some line this happens with the label up, some of them with the label down. Just make sure it comes off the spool in the same direction as you are reeling it onto the reel.

Hope this helps!