Forget the client's budget constraints
Introduction
Talk a lot about your agency history
Assume you know more than the client
Forget the client's budget constraints
Be oblivious to the client's other agencies
Ignore the RFP
Staff the pitch with who is available
Conclusion
Know what type of client you're pitching to because budgeting dependencies vary wildly between them.
If you are going to succeed in servicing a wide range of clients, understand that some of their businesses may be incompatible with your pricing model. If you cannot service a particular client or are unwilling to service a client under the budget they have specified, then do not just assume the budget can be expanded to conform to your business model.
If you decide to participate in a pitch, make sure you understand when the client's budget may be pliable. And if you really want their business, determine how you can adapt to service it.
Another question to ask is whether the brand is a traditional one that has gone online or is strictly an online brand? The differences that dictate the budget process within those companies are stark.
Traditional
A traditional brand, one with an actual, physical real-world product, like say, a sneaker company, has numerous ways it can adjust Operating Income Before Amortization (OIBA) to meet forecasts and run its business. It can cut manufacturing and operating plant costs. It can source another supplier who can provide higher-quality materials at a lower cost. It can shift to just-in-time delivery to shave warehouse costs, purchase in bulk, adjust distribution methods, packaging materials, shipping methods and sales cycles, as well as adjust headcount and marketing expense. All of this goes to the bottom line. That type of monetary flexibility enables more stable, larger retainer-based relationships.
Online
An online brand has considerably fewer ways to do this, and some, especially those in the service industries, usually have only two places to adjust OIBA: headcount, and marketing expense. The marketing budget for an online brand is much more flexible based on the brand's success, but much more rigidly tied to it. Online is held to a higher standard on direct business drivers due to the nature of much of the media and the degree to which it is trackable.
This means that it will usually have much smaller allowances for retainers and a tighter reign on project costs. However, the same flexibility traditional brands have in OIBA adjustment means that there are more diverse places for investment within the company, and thus places that eat up money when performance from an online campaign is contributing to the company's success. Online brands can more easily expand their marketing budgets based on campaign performance.
On the plus side, online brands are usually staffed with marketers who are steeped in internet marketing and technology. It's their business. Often on the traditional brand, although the team of online marketers is very savvy, they exist within an organization that is not. This usually requires longer approval processes, more "marketing by committee" and thus more agency personnel to staff the account.
Bottom line: Not all client business models, and thus budget models, can adapt to yours. Be more flexible and you'll fill those gaps you have in your client roster. Start small with online brands. Start with small teams, small retainers, small projects, and you will structure the account to grow based on their success.
Next: Be oblivious to the client's other agencies