Draft the trust deed to specifically state that the trust may be amended during the lifetime of the settlor. Although this is not an absolute requirement in every state, many states do require it, and in any case it removes any ambiguity that might become the subject of future litigation.
Include specific provisions on how to amend the trust within the text of the trust deed itself. These procedures can and should be simple--for example, a signed, notarized statement delivered to the trustee that specifies how the trust is to be amended should be sufficient to amend the trust.
Appoint a trustee who you are confident will follow your instructions without question. The trustee of a revocable trust is required to disburse the trust property as the settlor directs. Nevertheless, refusal by the trustee to do so in the case of an emotional family dispute, even in defiance of the law, could cause unnecessary delays and expenses.
Draft a written statement in which you specify the desired amendments to the trust. Sign this statement in the presence of a notary public. Deliver it personally to the trustee, or send it by registered letter, return receipt requested. Keep the return receipt for your records.
Draft, sign and date a codicil (amendment) to your will in which you specifically refer to the trust and set out the amendments you specified in the written statement you prepared in Step 4 above. Be sure to sign this codicil in the presence of two witnesses and have the witnesses sign the document as well. The purpose of this is to remove any legal ambiguity concerning your intention to amend the terms of the trust. A codicil to your will can also amend the trust even if the trust deed does not specify how the trust can be amended.