There is a book called Business and Legal Forms for Graphic Designers by Tad Crawford and Eva Doman Bruck that contains a number of boilerplate contracts that might be of interest to you. There is usually no need to consult a lawyer for simple contracts unless you need something absolutely bulletproof. A court will usually evaluate a contract the way a reasonable person would and consider intent in drafting to decide whether or not there's been a breach.

Although I wonder at the necessity of a NDA to protect techniques. Are you really doing something so amazing and revolutionary that disclosing it will hurt your business? The only reason to force a client not to disclose your source file is because it contains something that makes hiring you far better than hiring anybody else.