The lapels of your jacket should lay smoothly over your chest and, when buttoned, the jacket shouldn't bunch up or pucker out over your chest. Consider a shawl collar if you're feeling at all retro. Think Dean, James Dean.
The bow tie fits neatly over the tips of the wing collar shirt.
The shirt sleeves should extend one-half to three-quarters on an inch below your jacket's cuffs.
Your pants should just break over your shoe.
Always keep an eye on your cufflinks, button studs, and bow ties. They are easily lost when things get rowdy. The diligent best man will have an extra set in his pocket.
Remember, almost anything you do in a tux makes you look dangerously cool. Expect to get digits from all the pretty babies.
Consider renting and bringing an extra suit, and shoes just in case someone in the wedding party blows it. Conventional wisdom has it that someone probably will.
How To Tie a Bow Tie
1) Adjust the tie so that one end is slightly longer than the other, crossing the long end over the short.
2) Bring the long end through the center at the neck.
3) Form an angle loop with the short end of the tie crossing left. Drop the long end at the neck over this horizontal loop.
4) Form a similar angle loop with the loose long end of the tie and push this loop through the short loop.
5) Tighten the knot by adjusting the ends of both loops.
The formal bow tie-either hand-tied or with a band-should be of medium width and height, fitting neatly over the tips of the wing collar shirt. Ends may be pointed or square.