How is a pivot table created by Laravel?

Question

In Laravel 4, when working with many-to-many relationships as described in the 4.2 docs, how can I actually get Laravel to create the pivot table for me?

Do I need

Answer 1

To expand on Ben's answer (I tried to edit it but reviewers said it added too much):

To add the foreign key constraints, make sure if alpha id is unsigned, alpha_id is also unsigned in the pivot table. This migration would run after (2) in Ben's answer since it alters the table created then.

public function up()
{
    Schema::table('alpha_beta', function(Blueprint $table)
    {
        $table->foreign('alpha_id')->references('id')->on('alpha');
        $table->foreign('beta_id')->references('id')->on('beta');
    });
}