On the tenth anniversary or on the twenty-fifth are traditional, but you could renew them on any anniversary of your choosing.
No, but a lot of people like to do it to envoke those marriage day feelings once more.
By being good
The Gosselin's renewed their wedding vows in August 2008.
Jon and Kate renewed their wedding vows September 28, 2008.
Jon and Kate renewed their wedding vows August 8th 2008 at the Grand Wailea Resort on Maui, Hawaii.
If it still fits, you could wear your original wedding gown to renew your vows. Otherwise, just wear something classy and dressy, unless you're doing a themed renewal. Pick a color your spouse likes that makes you feel good.
No, the gifts are given as a boost to the new couple. You are not obligated by any means to provide a gift to a married couple that is renewing their vows.
To show there kids there undying love for each other.
During the Summer of 2008. I don't know the exact month or day.
Traditional wedding vows
Then they are different, additional vows.
If your anniversary does not fall on a Friday or Saturday then yes, you can renew your wedding vows on a different day. The date isn't as important and proudly saying your wedding vows a second time declaring your love for each other.
My parents renew their vows every five years.
Yes it does. If, for example, you were married in a civil ceremony, the Church does not recognize that as sacramental matrimony and you must 'regularize' that marriage with the Church by confirming your wedding vows before a priest or a deacon. Some couples who have been validly married in the Church for many years will renew their wedding vows also, even though they have been validly married for years.