It depends upon the project, the yarn, and the amount of yarn you have. <smile>
In addition to what you have listed, you can simply start knitting with the new yarn and plan to go back later to adjust tension and weave in the ends, you can do what is called the Russian Join [
www.geocities.com] (you can also google for videos), and the weaver's knot [
www.theropepeople.com] and for ribbon or tape yarn, sewing the ends of the old and new together.
I generally try to avoid knits but for some very fine yarns, or mohair which has a fine core surrounded by a lot of hair, and I'm in a hurry, I might knot my yarns together and even leave the ends loose if there is a true wrongside. If I have a two-sided project, I try to leave the ends loose and then duplicate stitch them into place later.