Before putting on your tie you should have your shirt buttoned up all the way to the top button and have the collar up. Starting the tying process with the wide end of the tie on the left or right side is just a matter of convention, so if you are more comfortable starting with the wide end on the left side then start from the left. Keep the knot of the tie tight throughout the tying process.
When you are finished tying your tie, put your collar down, the knot should be in the middle of your collar and the wide end of your tie should end around the middle of your belt buckle. If you don't get it right the first time simply unknot your tie and try again, tying a perfect knot on your necktie takes practice.
A good knot should always have a dimple. The dimple is the little indentation right below the knot of your tie. A good dimple is made before you tighten the knot. You start by putting your index finger in the fabric directly under the knot while lightly squeezing the side of the fabric as you tighten the knot by pulling down on the wide end of the tie. The dimple should be centered in the middle of your knot.