It's great to have an upright string bass in an ensemble and can add to the timbre and colors of the ensemble in the right places. You can always try to program music that has a bona fide string bass part. Alfred Reed has some good string bass parts.

Generally, they should always be bowing, perhaps unless there's some super short staccato sections where pizz would be more appropriate. There's really no 'tuning tendencies' concerns like there is with brass/woodwinds. I'd place them near the tubas / low WWs. I'd encourage them to 'dig in' in order to pull out a lot of sound in the band setting (if appropriate for the music).

Remember that string bass is a transposing instrument: the music is written up an octave from how it sounds, so tuba music would need to be transposed up an octave for it to come out/sound as written. Depending on the music you are playing, you could also give the student a bari sax part - just have them ignore the clef and add the equivalent of 3 flats (i.e. a key signature with 2 sharps turns into 1 flat; a key signature with 1 sharp would turn into 2 flats; a key signature with 0 sharps would turn into 0 flats; etc).

Good luck!