If you have minor children, naming a guardian for them is one of the most important considerations in your will. Typically, if one parent dies, the surviving parent will remain responsible for the children. However, complications arise if both parents die simultaneously or if one parent remarries. Unless you name guardians for your minor children in your will, the court decides who takes custody of the children in those situations.
If you have a spouse who is legally the mother or father of a child, then in most cases you should appoint the spouse as guardian. If you choose to appoint someone else, the court will balance your desires with the best interests of the children. For example, if you remarry and want your current spouse (and not the child's natural parent) to be the guardian, you may want to state your reasoning on why your current spouse would be better for the children. The LegalZoom Will gives you the option to write these instructions in the Special Directives Clause.
Guardians are responsible for a child's health, education and other daily needs. They are also responsible for managing a child's property (unless a testamentary trust has been created for the child - see the section on "Testamentary Trusts").