I normally include the following verbiage in contracts that I draft for clients...

INTEGRATION

This AGREEMENT represents the final and complete expression of the intent of the parties hereto. There are no other prior or contemporaneous oral or written agreements, covenants, representations, promises or undertakings other than those expressly contained herein upon which the parties hereto have relied. This AGREEMENT shall not be modified, amended nor supplemented except by written instrument duly executed by the parties hereto with the same formality with which they executed this AGREEMENT.

SEVERABILITY

In the event that any provision of this AGREEMENT shall be held to be illegal or unenforceable the applicable law shall immediately and/or retrospectively be substituted therefore, and the remainder of this AGREEMENT shall remain in full force and effect.

No breach or waiver of any provision contained herein shall be deemed to be a breach or waiver of any other provision contained herein.

CHOICE OF LAW AND FORUM

The validity of this AGREEMENT and the parties' obligations to perform hereunder shall be governed and construed in accord with the law of the State of ___________________________. Any and all disputes arising from this AGREEMENT, including but not limited to validity of this AGREEMENT and the parties' obligations to perform hereunder shall be litigated in the courts of the State of ________________________.
It is further understood and agreed that _____________________ shall be entitled to recover as part of his/her/its damages costs and expenses of litigation as well as reasonable attorney's fees.

ASSIGNMENT

This AGREEMENT shall not be sold, transferred nor assigned without the express written consent of the parties hereto.