Here is a step-by-step guide on how to tie a standard necktie knot:

1. Start with the wide end of the tie on your right and the narrow end on your left. The wide end should hang about 12 inches lower than the narrow end.
2. Cross the wide end over the narrow end.
3. Bring the wide end up through the loop.
4. Down through the neck loop.
5. Hold the knot loosely with your left hand and bring the wide end down through the knot in front.
6. Hold the knot with your right hand and bring the wide end up and over the knot towards your left shoulder.
7. Down through the knot again.
8. Tighten the knot by gently pulling on both ends.
9. Adjust the tie to your desired position by gently tugging at the knot and adjusting the position of the tie on your neck.

This method results in a standard, classic knot that works well for most occasions and collared shirts. There are several other knot styles, such as the Half Windsor, Full Windsor, or Four-in-Hand, which can be learned by following similar step-by-step instructions.