What contract provisions do you include in subcontract agreements (whether you're the primary or the sub)?
I use a simple agreement. It specifies the scope of work, fee for service, payment terms, and duration of the contract. The agreement also covers non-compete, confidentiality, work-for-hire considerations, and the sub's independent contractor status.
When I do subcontract, typically to build a team of which I am a part, I bind the subcontractors to my company's contract, then add as necessary any addenda regarding client-specific provisions. If a subcontractor is representing my company, they have to be on contract with my company.