In my experience, talismans and amulets are not particularly used in astrology. They certainly are not NECESSARY, although some people wear astrological glyphs and symbols as jewelry, the same way that a Christian wears a cross or girls wear heart earrings.
Basically, talismans are used to keep something away, amulets to bring something to you. You need to make the talisman or amulet in a form that is sympathetic with what you want, and the astrological sign that has influence over it. Charging during that sign makes it more powerful.