Many of the documents are intended more for General Contractors but you might want to look at some documents such as A105 and A107 from
http://documentsondemand.aia.org/. I believe that NSCA and InfoComm may also have some related resources for members, if you happen to be a member of either.
You may have to address issues such as if there are requirements relating to low voltage Contractor or Electrical contractor licensing, any insurance or bid/performance bond requirements, being able to pass through warranty on products (if you are not an authorized dealer and purchase equipment that you then resell to the church then the related warranty may lie with you rather than the church), sales tax for any equipment sold, etc.
Things to address in the Contract from your side include payment terms including any downpayment and/or retainage, site conditions (access, on-site storage, parking, deliveries and so forth), schedule and work hours required/allowed and ownership of any programming and documentation.
From the Owner's side the Contract should address not just what equipment is being provided and installed but also what the system will do, the warranty, the documentation and training to be provided and so on.
One of the aspects often left undefined is what determines the work being complete and the Contract fulfilled. I've seen Owners use final payment to extract work beyond that really in the Contract and I've seen Contractors asking for final payment before the system is finished and then walk away with it left unfinished if they get full payment. But even if both parties are operating in good faith there can be differences in what each sees as the work being complete and final payment due. The better you can define the work and when it would be complete, or what should be completed for an associated payment, the better for all parties.
People can get intimidated by complex, verbose Contracts with all sorts of legal language but I like to remind them that it often becomes a situation of dealing with that known amount of paperwork and legalese now or possibly dealing with an unknown, and likely much greater, amount later.
Beyond that, I agree with Tom. There may be state or local laws, project conditions, scopes of work, requirements, etc. that might be relevant to one Contract and not another.
You might also want to get yourself named as an insured on your subcontractors' insurance, that way in the unlikely event that something happens related to their work the claim can go direct to their coverage rather than through your coverage and then having to sue them.
