Unless you have a significant amount of experience in shopping for commercial real estate, it's a good idea to use a qualified real estate agent. Whether you are buying or leasing, an agent can help by pre-screening properties, which saves you time, and by negotiating on your behalf, which can save you money.
Typically the seller or landlord pays the agent's commission, which may raise some questions in your mind about the loyalty of the agent. However, keep in mind that the agent doesn't get paid until a deal that satisfies you both is negotiated.
You may opt to use a tenant's or buyer's agent, whom you pay yourself. In the real estate world, that's called tenant (or buyer) representation, a real estate specialty that is growing in popularity.