Everyone gets confused when its time to give a tip when they go out to dinner. That's no the only time you're expected to tip. Weddings have plenty of people to tip, so here's a general list of tipping percentages you should expect to pay:
Wedding planner - 10-20% of the entire bill for her services
Officient - $75 - $100 as a donation
Ceremony site staff - $20-$30
Organist / ceremony musicians - $20-$50 depending on length
Site manager for reception - 15-20% of bill for reception
Valet - $1 per car
Waiters - $20-$30 each depending on quality of service
Bartenders - 15% of liquor bill
Coat check - $1 per coat
Limousine - 15-20% of transportation bill (be careful in this situation because many already add a generous tip into the bill)
Delivery worker - $10 if just a drop off, $20 if drop off and set up
Tent assemblers or rental agencies - $20 each
Entertainers - $25-$30 each
Beautician and Barber - 15-20% of bill
Clean up crew - $20 each
Babysitter - $30-$40 plus a gift (more if longer than 5 hours or if caring for several children)