Here are some options, listed from least to most destructive/complex:
* Check for unlocked doors or windows: This sounds obvious, but it's the easiest and least damaging method. Try all doors and windows carefully.
* Slim Jim/Lock Pick: This requires specialized tools and skill. A slim jim can manipulate the locking mechanism, while lock picking requires more finesse. Improper use can damage the door lock. This is best left to a professional locksmith.
* Spare Key: Check obvious hiding spots – under floor mats, in the glove compartment (unlikely to be there if you lost the keys), or with trusted friends or family.
* Towing company: A reputable towing company may be able to assist in opening the van without causing damage.
* Locksmith: A locksmith is the best option if you need to get into the vehicle legally and without causing damage. They have the tools and expertise to open the van safely. They may require proof of ownership.
* Breaking a window: This is a last resort and should only be considered if absolutely necessary and you are the legal owner. It will result in damage and replacement costs. Consider the least visible window to minimize the damage.
Again, I strongly advise against attempting any method that could result in damage or illegal entry. Contacting a professional locksmith or the authorities is the responsible and legal course of action if you don't own the vehicle or are locked out.