In a previous blog post I discussed how your requirements effect the budget for your project. In this post we'll get more specific with time and money saving tips for working with developers, designers, or marketing firms.
This may sound counterintuitive but fixed priced contracts are always padded to cover the risk of bidding to low. Any work not agreed to will cost extra. Some firms will underbid a contract and simply not mention work they know you'll need. Latter you'll find out that work is "out of scope" and will cost extra.
Rather than a fixed price, ask for a rough estimate and agree to a hourly rate. Ask for monthly invoices and measure the effectiveness as you progress. With very little effort you should be able to tell how your money was spent, and how far you've gotten.
Cut down on overhead by combing tasks, meetings, and emails. It's far more efficient to work for several hours at once. Keep meetings short and only invite people who really need to attend. Try and gather information they'll need ahead of time so they don't have to stop and ask for it.
If you're working with a honest firm by the hour, you have nothing to fear. Many projects can be scaled up or down depending on budget, a good firm will advise you of all your options.