Of course, we try to recruit as many singers as possible. But sometimes getting a large group together is just not possible. Time, travel, distance, other commitments, family distractions, limited rehearsal space and scheduling, etc. --- there are always good reasons for people NOT to support choir. The trick is to figure out ways to help singers WANT to support Choir.
1. Get to know your possible singers. Find out their needs, time constraints, and desires. (Become their friend.)
2. Learn about their family situations that might play into when you might best schedule rehearsals. (Provide babysitting?)
3. Find out what styles of music they gravitate towards and how hard they are willing to work to perfect the singing.
4. Interview them about their musical abilities -- sight-reading skills, flexibility with singing parts, singing solos, etc.
5. Be sensitive to the needs and abilities of your accompanist. Choose music accordingly.
Armed with this information, you can make a plan. You will then be able to guess the level of difficulty you can use when choosing music. You can judge how many rehearsals it will take to reasonably learn the music. And you will be able to look for songs that will be appealing to the group.
It may be tempting to choose pieces that you sang in college with your a cappella choir or that you've heard the Tabernacle Choir sing. Be sure to check if those pieces could work for a small group. Many of those songs were written for hundreds of voices and full orchestras! The vocal parts may start out fairly simple but then suddenly break into a 4-part Men's section!
The trick is to have a selection of good stuff! Have a few pieces that are easy to learn in maybe one or two rehearsals. (Easy 2-Part Mixed Chorus) Then have a couple of challenge pieces or songs for a holiday coming up that might take longer but are really worth learning! Those are the pieces that the good singers will want to come for! Plan your rehearsals to always be working on several pieces and looking ahead to the harder things. Try to sing as often as possible.
Be patient. It takes some time to establish a good group.
Here is a piece that sounds more sophisticated than it really is. If you have a good accompanist with medium level skills, try this 2-Part Mixed Chorus arrangement of "Abide with Me 'tis Eventide."