Your project and the fabric you purchase will determine the choice of a needle and thread. If you are sewing a project requiring batting or a project which requires heavier fabric the choice of your needle will be totally different than compared to when you are sewing a fabric or project which is medium weight or light weight. Although most of the patterns do not mention the needle and thread size, the following guideline will help you make a fair choice of a needle and thread for any project.
1) There are three types of needles
Sharp point for woven fabrics
Ball point needles for knit fabrics
And wedge point needles for leather and vinyl material
2) Delicate fabrics like silk and lace need size 9 needle of Sharp Point needles
3) If your fabric is Light weight for example Chiffon, Organdy, Crepe or Batiste then the Sharp point needle size would be 11/80 and thread size would be 60.
4) For medium weight fabrics such as muslin, wool crepe, linen, gingham, gabardine, flannel or corduroy use Sharp point needle of size 14/90 and thread of size 50.
5) For medium to heavy fabrics like bonded woven, canvas, coating, denim, duck, sailcloth, or for projects with batting use needle of size 16/100 and thread size 40 or heavy duty thread.
6) Knits such as jersey tricot, bonded or double knits you need to use Ball Point needles which are specifically designed for knits and are available in sizes from 9 to 18 the larger the needle size, the more "rounded" the needle point is. Ball point needles push between the fabric yarn rather than cutting through the fabric yarn.
Before starting any new project always use a new needle and be sure to use the same size and type of thread in the bobbin as the top thread. For most fabrics cotton wrapped polyester size 50, thread can be used. If in doubt ask the stores clerk when you purchase the fabric on the size of the needle to be used.