Re: Which knots do you typically use ?
In the first case, I prefer a Blood Knot, or as an alternative, a Bimmini Twist for the salt.
In your second case, I increasingly have come to using a surgeons loop at both the leader and the tippet to allow for a loop-to-loop connection. (Sometimes the Perfection Loop on a heavier leader.)
All of this is, of course, relative. It's impossible for me to cover the exceptions; however, I must state, for the record, I am not a fan of the nail knot.