More is better.
You'll get faster coverage by planting small plants and spacing them close together than from larger, mature plants that are widely spaced. Plus, if a few plants die, a dense planting means others are nearby to fill in.
Coddle the young.
Even the hardiest groundcovers need help in the beginning. If the weather is dry, water frequently—1 inch a week.
Patrol for weeds.
While your plants are still getting established, check them frequently and pull out any weeds. Use a dandelion weeder to get the whole root. Don't rely on weed cloth; it's not always effective.
Keep rodents away.
Where rats and mice are a problem, opt for deciduous, nonvining varieties. Many types of evergreen ivy, for instance, provide a thick blanket of year-round cover—ideal for nesting—and can even serve as a ladder into nearby trees.