You can do some stretches before you warm up. Stretch the neck around in all 4 directions individually, and then roll it around a bit clockwise and the counterclockwise. Don't go to too much extreme, just feel the muscles getting a slight pull. Then you can stretch your jaw out in a similar fashion although I would recommend doing it very lightly with the jaw as the jaw, unlike most other joints, is rather easily unhinged. Some people like to do shoulder stretches by rotating their shoulders and then swinging their arms around a bit. You might want to do similar stretching for your tongue even.
Something that helps me release throat tension is something Mr. Vendera put in his RYV book. Sing very lightly through a few songs. The light and quiet tone will allow you to sing with very little tension due to the lack of intensity. Don't worry if the tone of your voice seems to change drastically with you ascend doing this sort of warm up exercise. We are just interested in keeping tension out of the throat.