The two primary mechanisms involve allowing putative class members to either opt out of or opt in to class membership.
Opt-out classes, which include all members who do not opt out, tend to be more inclusive than opt-in classes, which include only members who affirmatively opt in. Because of inertia, an opt-in regime would result in "drastically reduce[d]" numbers of class members.
Those who want to opt in are likely to do so, and the class then will be composed of only those claimants who have expressly consented to aggregate litigation.
And self-identification in an opt-in class in which only those who opt in are potentially included in the class gives both the court and the defendant an effective opportunity to determine whether those who have opted in really do fit within the class definition.
As long as the number of class members who opt in exceeds around forty, (138) and as long as joining them together would be impracticable, then the class will have met the numerosity requirement.
Don't make it appear as though checks or recurring debits won't be covered if the customer doesn't opt in to the ATM/debit card program.
Don't trick them--don't imply that their ATM/debit card won't work unless they opt in, and don't offer better account terms if they do (that is a violation of the rule).
I "opt in" because I Want to know when the Gucci Hobo Bag is discounted, if ever.
For example, let's say I visit a site that sells vitamins and I opt in to receive additional information.