When buying an external vibrator, here are some steps you can follow:

1. Research: Do some research to learn about the different types of external vibrators available, their features, and their price ranges. Read reviews from other users to get an idea of what people like and don't like about different models.
2. Decide on your preferences: Consider the factors mentioned earlier, such as type, power and intensity, size and shape, material, features, and your budget, to determine what you want in an external vibrator.
3. Choose a reputable retailer: Look for a reputable retailer that specializes in sex toys and has a good reputation for customer service and discretion. You can also buy online, but make sure you choose a trusted website with secure payment options.
4. Check the product description: Before making a purchase, read the product description carefully to ensure that the vibrator meets your needs and preferences. Pay attention to the dimensions, material, power source, and any additional features.
5. Consider the packaging and shipping: If discretion is important to you, choose a retailer that ships in discreet packaging or offers in-store pickup. Check the shipping times and fees, as well as the return policy, in case you need to return the product.
6. Use and care: Once you have your vibrator, make sure to follow the instructions for use and care. Clean the device before and after each use, and store it in a cool, dry place. Replace batteries or recharge the device as needed.

Remember, buying a vibrator is a personal decision, and you should choose a device that fits your preferences and needs. Be safe and have fun!