The biggest mistakes SMB owners make when networking are in approaching everyone and hoping to make a sale. You do not sell at networking events, and you prioritize quality over quantity—it's better to make a few, good connections.
When you approach someone at a networking event, you should strive to be interested, not interesting. Talk less about yourself. Get the other person to talk about themselves, and ask questions about them. Also, summarize back to them what they just told you.
Then, within 24 hours of the event, follow up with them. Invite them out for coffee, or send them an interesting article. At that point, you need to nurture them as any other lead, connection, or friend.