I recommend that you scald and sterilise bottles and teets until your baby is 6 months old. You can scald the bottles in a kettle full of boiling water. After purchase, unscrew the bottles, wash them with warm water and washing-up liquid, and rinse thoroughly. Boil it for 5 minutes.
After next feedings it will be enough to pour the bottle with boiling water (and remove food leftovers with a brush).
You can use a microwave steriliser or steam steriliser, which don't damage the bottles as badly as boiling. Thanks to sterilising, you can be absolutely sure that the bottles are perfectly clean and sterile. Sterilising is necessary, as all dangerous germs are only destroyed at the temperature of 100C. Sterilising protects your baby from food poisoning. Bottles remain sterile for about 3 hours after sterilisation if you use a steriliser.