First you must be willing to hire a consultant strong in what you are weak in with enough character to represent your interests. This is a challenge on small projects where there is temptation save money due to a small budget.
There is a saying that goes as follows; a smart person learns from their experience but a genius learns from others. Hiring a consultant who has experience in what you are about to do is a great way to minimize your risk of the unknown.
With experience the consultant will be familiar with the ins and outs associated with your project and the common pitfalls. How do you deal with change orders? How do you review the plans and ensure conformance? How do you test the materials incorporated? What electronic records need to be kept? How do you review the schedule and approve or reject time extensions?
You will want someone who will communicate early, often and clearly with all stakeholders. Doing so will minimize having your expectations not met and the frustration associated with it. It also is appreciated by the contracting community if you are upfront in what you are looking for and how you will measure it.
With all of the above it goes without saying you want someone who can deal with all of the personalities on a project. It is never easy to reject materials or direct contractor replacement of work performed but you also do not want to escalate the problem such that the rest of the project is compromised. This too comes from experience. Usually there is a reasonable solution all parties can agree to and avoid a contract claim.
Feel free to contact me if you need advice on selecting a consultant.