First, remember that tipping is ultimately up to you. If a vendor does a good job then you want to show your appreciation. Conversely, if you are not happy with the level of service from a vendor than you have every right to choose not to tip them.
As you are budgeting make sure you read the fine print on all your contracts (please please do this before you sign!!). Most of the 'big' expenses build gratuity into their contracts. Especially the catering/wait staff.
This is just a *sample* of tipping guidelines. Again, the people you tip and the amount you choose to tip is up to you!
Limo Drivers: 10 to 15% given once service is rendered
DJs: $25 to $75
Wait Staff: 15%
Bartenders: 10% of bar bill (eek!)
Hair Stylist: 15%
Wedding Coordinator: $50
Wedding Planner: 10% of fee
Ceremony Musicians: $5 to $10 per musician
Banquet or catering: $50 to $100 (to be divided out by catering captain)
Photographer/videographer: (if owner tipping is optional) $50
Flowers: $10 to $20 per person delivery
Always send a thank you note to your vendors. A letter of recommendation is also greatly appreciated.