I know this has probably been covered, but I couldn't find it with the search feature. I have spent the winter learning to operate my first baitcaster, that along with several snags has left me with about half a spool of line left on the reel.

Should I take this line off, and totally re-spool the reel; leave this line on and spool up the rest of the way with new line; or continue using it like it is until I just don't have enough line to fish with?

You can use what 's left in the reel as backing and fill with fresh line. It 's not good to fish with half of the spool filled, the line is so tightly coiled that it will be like fsihing with a slinky.

Do you just use a surgeon's knot to conect the new to the old?

Tie on the new line with a uni/uni knot or something similar and spool up from there like Raul suggested. 

Ok, thanks!

Never respool with new line, always use what you have for backing, and save some $$$.

X 2 re: the uni to uni knot.