Yes, you can.
There are many sample documents available at bookstores, libraries and even on the Internet.
However, if you try to do your own trust or estate planning documents and you die or become disabled in the process, you will not have another chance to fix them. You want to be sure you have not surpassed any loopholes and your affairs are completely in order.
If you do make your own estate plan, at the very least, meet with an elder law attorney to make sure you are all set and you have not left any gaping holes that could leave your family in a financial lurch.