Do I need to file a NOF?

This is in Michigan*

Michigan law does not allow construction liens against public property. 

If Saginaw County is the Owner, and the GC has provided you with payment and performance bonds, this is a public project. Your rights lie with the payment bond. 

Under Section 7 of the Public Works Bond Act (MCL 129.207 - http://legislature.mi.gov/doc.aspx?mcl-129-207), the notice requirements depend on your contractual relationship with the bond principal (usually the GC). If you have a direct relationship, such as a subcontractor or direct supplier, a first Notice of Furnishing is not required. But if you do NOT have a direct relationship, you must serve a Notice of Furnishing within 30 days after furnishing your first labor or material. 

This first notice must be served on the principal contractor by certified mail. I usually also copy the surety, public owner and the person you have a contract with. That is, if you're a supplier to subcontractor, I would serve notice on the GC, surety, owner and subcontractor. All by certified mail. 

Here's the full language of Section 7: 

"A claimant not having a direct contractual relationship with the principal contractor shall not have a right of action upon the payment bond unless (a) he has within 30 days after furnishing the first of such material or performing the first of such labor, served on the principal contractor a written notice, which shall inform the principal of the nature of the materials being furnished or to be furnished, or labor being performed or to be
performed and identifying the party contracting for such labor or materials and the site for the performance of such labor or the delivery of such materials, and (b) he has given written notice to the principal contractor and the governmental unit involved within 90 days from the date on which the claimant performed the last of the labor or furnished or supplied the last of the material for which the claim is made, stating with substantial accuracy the amount claimed and the name of the party to whom the material was furnished or supplied or for whom the labor was done or performed. Each notice shall be served by mailing the
same by certified mail, postage prepaid, in an envelope addressed to the principal contractor, the governmental unit involved, at any place at which said parties maintain a business or residence. The principal contractor shall not be required to make payment to a subcontractor of sums due from the subcontractor to parties performing labor or furnishing materials or supplies, except upon the receipt of the written orders of such parties to pay to the subcontractor the sums due such parties."

A second notice should be sent within 90 days after you last furnished labor or materials, if you're still unpaid, stating what is owed and including a demand for payment. Send this notice to the same parties: bond principal (GC), surety, public owner and subcontractor (if you're a supplier). 

I believe LevelSet has the notice forms required for public projects in Michigan.