What wedding vendors should I tip and/or feed?

Your already paying your vendors for their services, be it the florist, the photographer, or the DJ.  But you also don't want to be "that bride", the one who doesn't tip or feed the vendors that are normally given gratuity.  So how do you determine who gets tipped and who you should feed?
A general rule of thumb, like in any other service-related industry, is to tip vendors that you believe have done a great job or have exceeded your expectations.  Unlike a waiter or waitress who earn low wages and depend on their tips to make a living, most professional wedding vendors are making a living off of the prices of their package.  And while tips are nice and always welcomed, they are not a necessity to survive.
 

You should first check your contract with each vendor, especially the Reception Hall, as often times gratuity is already included in the price.  For some of the less expensive services, such as make-up, a normal 10%-20% gratuity is acceptable.  But for bigger ticket items such as your Hall, or Photographer, a 20% tip could be hundreds of extra dollars!  For these more expensive vendors, maybe there are other ways you can show your appreciation:  a gift, an extra $50-$100 in cash, or how about dinner at your Reception?
Speaking of dinner, you want to keep in mind that your vendors should be treated like professionals, and it is standard to offer them some food.  In the case of your photographer and/or videographer, sometimes these vendors are starting their day at your house in the morning, and are with you all day long.  You can't expect them to do their job al the way until the end of the night without eating!  To not be fed at all is very rare for a photographer or videographer, as at the very least they are normally given a "less expensive" meal during dinner (while your guests, for example, chow on filet mignon the vendors are served a sandwich).  While this is somewhat common, and sometimes even suggested by the Reception Hall as a way to save a few bucks, it is recommended that you feed your vendors a meal as if they were a guest at your wedding.  Overall, you will get better service and they will feel like you were really looking out for them.
Dedicating one table, maybe in the back of the room for the vendors is very common.  Be sure to find out how many people there are:  how many band members?  Does the DJ have an assistant?  Are there more than one photographer or videographer?  Keep in mind that you should only feed those whom you paid for to be at your wedding:  you shouldn't have to feed 3 of the DJ's friends and the Lead Singer's girlfriend!