This question comes in several forms, but it usually boils down to, "Why does membership matter?"
More than anything, membership is about 3 things:
1. Letting people know who you are as a church
2. Seeing if they align with where you're headed
3. Establishing a baseline of what it means to be committed at your church
Your membership class should deal with these 3 issues in depth and then your membership follow up should be checking to make sure all of your members are fulfilling the covenant you agreed on.
If you don't do these things, them membership isn't going to matter. People may go through your class, but no one will take it seriously.
For a resource that contains everything you need to develop a strong membership system, check out The Complete Membership System.
P.S. To save 20% on our membership resource, use the coupon code member2010