Sterilising what, when and how
Small babies are very susceptible to germs and because milk is an ideal breeding ground, the best way to keep germs at bay is to sterilise your babys feeding equipment. Its particularly important to sterilise any bottles that will be used for milk if youre making up a full 24 hours worth of feeds. If you put milk into a grubby bottle, germs will start multiplying as soon as you add warm milk. If the grubby bottle happens to be the last of the batch that you use, the germs will have had time to multiply to a dangerous level by the time you give it to your baby.
In theory it would be perfectly safe not to sterilise a bottle providing you wash it thoroughly and use it immediately. The reason I say in theory is because peoples knowledge of hygiene varies, and your idea of washing thoroughly may not be the same as mine.
Having said this, theres some concern that mothers are creating problems for the future by being too meticulous and over-protecting their babies. So I would suggest that if you need something in an emergency (such as a nipple shield), its OK not to sterilise it. You could wash it thoroughly in hot soapy water, rinse it under the tap, dry it with a piece of clean kitchen paper and then use it immediately.
Ways to sterilise
If youre fully bottle feeding it makes sense to buy a proper steriliser so that you can sterilise lots of bottles at once.
If youre planning to breast feed its still worth having some sterilising equipment, but you wont need to invest in anything sophisticated or expensive.