How do we ensure that teethers n toys are clean and safe for the babies since they like put everything into their mouth?

Once a week for me with just dishwashing sopa under running water:-) Toys that are kept at home stays at home. When we come back from outside, we always wash our hands. I don't keep my kids' toys too clean because some germs are good for their immunity. If the toy looks "yucky" then clean it immediately. If you have someone come over to play with your kids, then wash it afterwards. But if the toy is only played by your kid at home, I wouldn't worry about too much germs :-)