The most secure garage lock is one which is applied inside and has no outside keyway.

Garage door openers are vulnerable to manipulation with electronic devices. The current multi-channel, owner-selectable coding, devices are best and will resist this. For additional security, it should be turned off, or unplugged, for vacations. Make sure there is no outside button. If there is, disconnect it.

Garage side doors are often outside the fence line, and if they have windows, anyone can 'casually' look into the garage and assume that there's no one home if there's no vehicle inside. Ensure that, if there's a side door to the garage, it's a solid-core wood or metal door. It should be equipped with a deadbolt lock that has an inside keyway (to prevent operation from the outside). If building a new home, consideration should be given to putting in a windowless garage side door, and use better illumination inside.

If the attic access is in the garage, equip it with a lock.