Depends on what type of knot you are going for, and if you are tying it on yourself or someone else. If you are tying it on yourself, here is an easy way to tie a basic tie assuming you are right handed:
Place the tie around your neck, right side up (design facing out, seam against your chest) so that both tips are pointing down and so the wide side is on your left and lower than the narrow end by a couple inches. Cross the wide end over the narrow end, making an X near your neck. Then, pinch the crossing point between your thumb and 2 fingers with your left hand. Your fingers and thumb should be pointing up at your face. Circle the wide end clockwise all the way around the narrow end, over your thumb and fingers, but don't put it through the 'V'. Bring the wide end up through the 'V' from the back. Then push the wide end through the space where your fingers are. You will need to pull and tug either end in order to tighten the tie and adjust the narrow and the wide ends so that they lay properly down your chest. The wide end should be longer than the narrow end, it should be hidden behind the wider end but the wide end should not hang any lower than your belt line when you are standing.
You may need to practice a couple of times to get the hang of it.