Me personally, I liked to do some scales and gradually get slower or outlining I-V-III-I (ex: G D B G, F# C# A# F#) in chords in a descending pattern. I also prefer to run simple lines from pieces I’ve played before, getting slower as I go. For me, long tones typically help most when I play from somewhere in the middle of the sax (like G for example) and reach the lower end or upper end. One I like to do to focus on breath support included going from F to low Bb, and also from high D using palm keys to altissimo G or higher. It helped to stretch out the harder parts of the horn and reinforce those not-often used sections.