Knowing what to wear to a wedding falls under three basic principles that apply across the board no matter what wedding you will be attending. Understanding these principles will serve you well and allow you to enjoy the day rather than worry about whether or not your wardrobe is appropriate.
Knowing the dress code for the event is the first step in knowing what you should wear. More than likely this information will be furnished within the wedding invitation and indicate either formal, semi formal or casual. If this information is not made available then feel free to ask a member of the bridal party or someone connected with the wedding planning.
For a formal wedding a tuxedo is ideal though in today's day and age a dark suit is also acceptable. Essentially choose whichever garment you already own, and if you own neither rent a tuxedo. For more information, you may also want to read our guide to black tie attire.
If the wedding is semi formal then you should either wear a suit or a sport coat. There is no real ideal here, and either is appropriate; so choose whichever garment you are more comfortable in and looks the best. For more information, you may want to read our guide on Semi-Formal Attire.
For a casual wedding either a sport coat or polo shirt would be equally appropriate. Again there is no right or wrong choice here and it all depends on the venue and any indication you have been given from someone who is planning the event. If you are unsure, wearing a sport coat is always the safer bet as it is far better to be slightly overdressed than woefully underdressed for this type of occasion.
As with any dress event you're going to want to accessorize to a level that matches your outfit. Cuff links are only appropriate with formal attire and would look silly when worn with a sport coat. Similarly, make sure you are wearing the right type of shoe to match your outfit; and no matter how casual the wedding, remember that sneakers are never appropriate.
Knowing the wedding venue will help you make a decision about what type of clothing will be appropriate. For instance if the reception is being held in a ballroom yet the invitation indicates semi formal attire you should probably make the assumption that the wedding couple is being polite and not requiring that everyone rent a tuxedo; however a tuxedo is definitely appropriate for a ballroom venue.
If you are attending a semi formal outdoor wedding and are not sure whether you should go with a sport coat or suit it is safe to assume that a lower tier of formality is appropriate and wear a sport coat. Additionally for outdoor events it is safe to break the tradition of wearing dark colored sport coats; and instead choose a jacket made out of lighter materials such as cream or khaki colored cotton which pairs nicely with a pressed pair of khakis. Just remember; never wear the same shade of khaki for both your jacket and trousers –unless you prefer to look like Panama Jack.
Lastly you'll want to take into consideration what your partner will be wearing to the wedding. It is important that both of you dress to the same level of formality. Few things look as silly as when a woman shows up in a tailored evening gown and her date is wearing a polo shirt.
It is not necessary that you match the colors of each other's outfits (which in fact can be quite tacky) however it is good to have the colors complement each other ex: if your date is wearing a green dress do not wear a red tie etc.