Choose the pricing model first
Fixed price works when the spec is clear and stable; you carry the estimation risk, so price in a buffer. Time and materials works when requirements will evolve; the client carries the risk, so report hours weekly. Many developers use fixed price for a defined first version and T&M afterwards.
Define 'done' with acceptance testing
List the features, then state how they're accepted: the client tests within 5-10 business days, reports defects in writing, and anything not reported counts as accepted. Without this, a project can stay "almost finished" forever.
Bugs, warranty and maintenance
Offer a short warranty (e.g. 30 days) to fix defects against the agreed spec, free. New features and changes after that are paid work, ideally under a website maintenance agreement or a retainer.
Code ownership and third-party code
Transfer ownership of custom code on final payment, keep your reusable libraries, and note that open-source components stay under their own licences. Templates: fixed-price software, web development, mobile app. Draft it now with Clinch: describe the job in a sentence, get a clean draft, send one link. Your client signs from their phone without an account, and the deposit is paid in the same step.