I was in a similar situation six months ago when I got my license. Do you all subscribe to a data service like Costar? It can be a great list building tool, and the reps can give you good advice on how to go about targeting specific market niches.
When I first started and didn't have access to Costar I compiled lists of businesses using Hoover's, Google, etc. that had some relation to my own personal or professional background. I used that as my call list. My broker fed me a few leads to get me started and I was able to establish a focus area for myself based on my interests and skill set. The brokerage itself doesn't have a particular focus on any one commercial asset class, but the individual agents all have their own niche. We're a small shop so it works well for everyone.
In terms of sourcing deals I think @Jacob Wathen's suggestion is a good one: get out into the community and make yourself known. Going door to door is definitely one option. I also attend various small business networking events, startup conventions, and chamber of commerce events. One good approach for us has been to work closely with our local economic development organization so that they feed us leads whenever small businesses come to them for startup help or out of state businesses contact them about relocating. In terms of investment sales, holding seminars or information sessions targeting specific demographics that are likely to invest in real estate is a great way to provide value and hopefully capture some of that market share. Setting up some type of direct mail campaign targeting small business owners and investors might also be another strategy. The possibilities are only limited by your creativity.