I think there are three ways to go with
business development for architects.
Although there are three ways, focusing on just one lets you get good at it. Trying to use all three will be confusing for you and for your potential clients. Moreover you are not likely to be successful in any one of them, and spend too much time and money in the attempt.
The Way Of The RFP
Responding to Requests For Proposals is rarely a system that works well for small firms. There is usually a focus on 'head count' that the small firm will lose. Also the expectation that you have recently completed several similar projects is not likely in a small firm. But the overhead required by responding to RFPs definitely makes this a large firm strategy. The RFP selection process has a tendency to treat responders as commodities, so you need a large volume of work to be profitable - another big firm characteristic. This is your father's Way, but it will be around as long as there are institutions.
The Way Of Relationships
This strategy can work for any size firm. Social Media and electronic media are tools that support this strategy. You need to stay in touch with all the folks who have work that you want to do. Get to know them. Then find a way to help them so you are the go-to firm when the need arises. Social connections help. A small firm can easily afford this approach. In a good economy, you may never compete with the big firms with this Way. Check out my six-step system here.
The Way Of The Niche
The barrier to developing a niche used to be the high price and difficulty of establishing your expertise in the minds of your potential clients. Brochures, mailings, conventions, face to face meetings were the tools you needed. Now the main tool is writing a blog to showcase your expertise with a business/building type. So what once was a large firm strategy because of the cost can now be pursued by anybody. The Niche Way takes time, but the longer you pursue the niche, the easier it gets. Competition fades, and profits rise. You can find a bit more about developing a niche here.
This article about the 4 Value Propositions for ANY business might give you some ideas on how to differentiate yourself once you have chosen a business development 'Way'. However, not all value propositions apply to each of the three 'Ways'.