So you've been invited to a traditional Chinese wedding and you're all excited. It's an exotic experience that few in the West have the opportunity to attend, and you're already mentally fitting yourself into a slinky red dress (or cool Sun Yat Sen suit) when suddenly the question comes up: What kinds of gifts do people bring to these things anyway? While there is no unified set of rules for giving gifts in a Chinese wedding, some general guidelines do apply.
First, and most importantly, you will most likely not be expected to give a "gift" as such, but rather a red pocket, which is a lucky red envelope filled with money. Most stationery stores in China sell red pockets, and you will be expected to provide your own—the bride and groom won't give you one to fill. Your gift should be in the currency of the wedding locale, unless the bride and groom specify otherwise. The amount of money is where things get tricky.
The low end is easy to determine--you should never give a red pocket without the equivalent of at least $60 (U.S). If you give less than that, it is considered extremely rude, as it gives the impression that you don't really care about the couple and are just coming to the wedding for the free food. One of the quickest ways to lose a friend is to give an extremely small amount in a red pocket, and the bride and groom will know who slacked off--receptionists at the door take the red pockets and open them while the wedding is going on, writing down how much everyone gives.
Other than that, the amount of money you give is determined by the closeness of your relationship with the couple. For acquaintance level friends, an amount of $60 is perfectly acceptable. For closer friends, anywhere from $75 to $85 is a better bet, give or take a bit, and for very close friends, a pocket amount of around $100 is good. However, there is no limit on how much you can give in the red pocket, if you have the extra money and feel like giving more, the bride and groom always appreciate it, as red pocket money goes to offset the cost of the wedding banquet. Some gifts even range into thousands of dollars, although this is certainly not expected.
Even if you receive an invitation and decide not to go, it is best to send a pocket with at least $30 to show your sincerity in congratulating the couple. However, it is not unheard of for people to throw away invitations and say they never got them in order to not send the money.
After you decide the general amount you want to give, another factor comes into play--lucky numbers. This is easier to do in currencies that work with larger amounts of money, for example, Hong Kong dollars or ren min bi. The two major lucky numbers for red pockets are six and eight, because the word for six sounds likes the Chinese word for "never ending" and the word for eight sounds like the Chinese word for "money". By giving money in amounts that end in six or eight, or have multiple sixes and eights in them (686, 888, etc.) you are showing your wish for the couple to always be happy and wealthy. Even if you can't give money that ends in a six or eight, red pockets should always consist of even amounts of money, because they represent pairs. Even numbers can be divided by two, just like the two people coming together in the wedding. So while 686 would be preferable, 602 would also be acceptable, since it is even.
However, zero, one and four are unlucky, and your red pocket should avoid them at all costs, as zero reminds people of endings, one represents being single, and the word for four sounds like "death". For example, a combination of 404 would be particularly bad, or 101. All odd amounts are generally bad, because they are associated with funerals. None of this is hard and fast, and giving an odd-numbered amount is better than giving none at all, but even numbers are much better, as they remind the bride and groom of being part of a pair.
Aside from these general rules, the rest is up to you. Giving a red pocket is a practice largely dictated by convention, and as long as you give an acceptable amount, without any overtly negative numbers, your gift will go down just as well as the fabulous yu zhu served at the wedding, and you will have the satisfaction of knowing that you can give a traditional gift like a native Chinese.