When singers have trouble correctly ending a vocal melody, it can disrupt the flow of the song and distract other singers. By running through each line individually you can highlight exactly the right part of the measure where you want the singer to end. Choral conductor Drew Collins recommends getting the singers to snap their fingers to punctuate the end of their phrase. Split the choral group up according to which part they are singing; snap your fingers at the exact moment that you want each vocal phrase to end. Then have your singers do the same. Run through the song with no accompaniment a few times have your singers perform an exaggerated finger snap right at the end of their phrase.
Delivery is an important element of choral performance, especially in styles such as Gospel and worship music in which accompanying hand movements help engage the audience. By placing some full-length mirrors in front of your choral singers during rehearsals you can help them refine their delivery technique. They'll be able to see one another from the front, rather than just from behind or the side as is typical during rehearsals. Stand at the back of the group, on a step if necessary, and conduct from behind. Make eye-contact with the singers via the mirror.
Have the baritones sing the soprano melody and vice-versa, but in their own register, so the baritones are singing a low version of the soprano melody and the sopranos are singing a high version of the baritone line. This gives the singers a greater understanding of what the other singers are doing and how the individual parts relate to one another. Use this as a warm-up exercise or rehearsal technique, but be careful that the singers don't loose focus of their own parts.
When tackling particularly complex or challenging parts, focus just on the beats. Write the rhythm out on a single line on the staff and instruct the choir to sing it in monotone. While they aren't worrying about pitches, they can focus on the rhythmic patterns.