If you are currently the trustee, you need to be administering the estate NOW, meaning you need to manage the assets and liabilities of the trust, and prepare any necessary accountings and tax returns.
There are lots of guides that can give you general information on the job of being a trustee. There is no guide that can give you specific advice as to your particular trust, given that the terms, assets, and liabilities of every trust are different.
If the assets are significant, then you should meet with an attorney who can help you with the legal aspects of trust management. The trust will be responsible for covering the attorney's fees for these services.
I agree with the previous post. You have specific duties and responsibilities now as the Trustee. More duties are imposed when the Settlor dies and the Trust become Irrevocable. Many guides are out on the internet that can provide guidance. I can send you our general letter outline we provide. But, as the previous post states, it will not provide any legal advice. The devil is in the details.
If you are the presently-serving trustee, you should be administering the trust according to its terms right now, presumably using the trust assets for the benefit of the settlor as set forth in the trust instrument. You may or may not be the trustee at the settlor's death, depending on what the trust itself says. It is possible that the trust requires someone other than you to assume the role of trustee on the settlor's death. In any event, as trustee, you should make sure you are familiar with the trust assets, how they are being managed, etc. The best source for guidance on what your duties are now, and what they will be when the settlor dies, is an experienced trust and estate administration attorney in your jurisdiction.
This general response is not intended to create an attorney-client relationship.