Zeta Sagittarii (Ascella, the Archer's Armpit) is the southern-most star in the central trapezoid, which is the most notable asterism in this constellation. Some observers call this asterism a teapot.
     To locate this trapezoid draw two lines, one straight south from Altair and the other east from Antares; they meet just east of the trapezoid: binoculars.
     It is also found due east of delta Sagittarii one binocular field of view and a bit more.

All four stars which form the trapezoid are found here, confirming that you are indeed in the middle of Sagittarius. Sigma Sgr is ‘Nunki’, the Archer's hand as it aims the arrow.

With the naked eye, from this trapezoid you should be able to pick out the three stars to the west that make a vertical curving line -- the Archer's bow.