Independent Contractor Agreement
As you might know, as an independent contractor (IC or consultant) you are not an "employee" under employment and labor laws. So, you don't have employee rights per se.
But you do have independent contractor rights, such as those under relevant employment and labor laws that prohibit your clients from controlling you as an employee. (See Independent Contractor vs Employee for more information.)
To help ensure such rights, you'd be wise to work under a legally-sound, independent contractor agreement. Doing so will also grant you rights under contract law. Always get the terms of your IC employment in writing, signed and dated by you and your clients.
You may write your own independent contractor agreement. But, if you don't feel comfortable doing it yourself, ask an attorney to custom-tailor one for you.
If you prefer doing it yourself, consider purchasing a standard, customizable, independent contractor agreement and an authoritative book on the matter. Still, it's a good idea to at least ask an attorney to double-check your work.
When creating your independent contractor agreement, make sure that you cover every contingency for the types of projects you complete for your clients. If you don't feel comfortable determining all contingencies on your own, again, it's a good idea to ask an attorney to double-check your work.
Some of your clients might insist on using their own independent contractor agreements. It's a good idea to ask an attorney to double-check them too before you sign, to make sure that they're not more to your clients' advantage than yours.
Of course, it'll likely cost a fee to consult an attorney about an independent contractor agreement for any reason. (It might cost less to have an attorney simply check an agreement, verses writing one from scratch.) But, doing so up front could save you much heartache and even larger legal fees down the road, should legal problems arise.
Another advantage is that the attorney's fee is likely to be a tax-deductible business expense. The same goes for the cost of a standard independent contractor agreement or an authoritative book on the matter.