Through the use of a base equal in strength.
Acids are substances that are high in pH. Anywhere from 0-7 is considered acidic.
In order to neutralize an acid, a base is required. However, a certain procedure is necessary.
Depending on the strength of the acid, a base of equal strength is required.
For example, to neutralize a weak acid, you need a weak base. If you would use a strong base, then the solution would become basic, rather than neutral. Same goes for strong acids - need a strong base.
This also applies if you want to neutralize a base, use an acid of equal strength.
Hope this helps :)