Magnets should be stored in pairs with their opposite poles lying side by side.

Explanation

### Step-by-Step Solution:

1. **Understanding Magnets**: Magnets have two poles - a north pole and a south pole. These poles exhibit magnetic properties, where opposite poles attract each other and like poles repel each other.

2. **Storing Magnets**: When storing magnets, it is essential to arrange them in a way that maintains their magnetic properties and prevents them from losing strength or getting damaged.

3. **Pairing Opposite Poles**: To store magnets effectively, they should be placed in pairs with their opposite poles (north and south) lying next to each other. This arrangement helps in maintaining the magnetic field and prevents the magnets from repelling each other.

4. **Benefits of Proper Storage**: Storing magnets in this manner prevents them from becoming demagnetized or damaged. It also makes it easier to handle and use them when needed.

5. **Conclusion**: Therefore, the correct way to store magnets is in pairs with their opposite poles lying side by side. This practice ensures the longevity and effectiveness of the magnets.