When building business relationships, it is important to be thinking about synergies and ways to assist one another. As you feel comfortable with certain people, you should discuss ways in which you can work together. Rather than selling your services / products to one another, you can form a strategic relationship.
Strategic relationships have both parties in mind so you both can benefit at the same time. Figure out what type of relationship you want to have such as referral partners, event sponsors, business partners, etc. Once you decide on the strategy that works for both of you, then you can take your relationship to the next level.
Spend time putting a plan together as to how you will assist one another. For some relationships, you may form an exclusive arrangement where you will only send prospective clients to your strategic partner. For other relationships, you may cross promote each others' services at an event or in marketing materials. While with other relationships, you may pursue clients together in one proposal.
Over time, these relationship will flourish if nurtured properly and effectively. Having these type of strategic partners in your network is critical to making things happen. Take some of your relationships to the next level by matching synergies and goals so you can grow strategically together.