Simply replace the unfilled areas such as "__" and "_[date]_" with your information.
To Whom It May Concern:
[Name of babysitter] has been caring for our [children/child] for [length of time] now. [He/She] has always been tremendously responsible, and our [children/child] have always seemed to enjoy the time spent with [his/her/their] babysitter. [He/She] does not simply sit and watch television, ignoring our [children/child], but always interacts and spends time with [him/her/them].
[Name of babysitter] is kind, communicative, and trustworthy. We know that we can leave our [children/child] in safety, and always enjoy the time we have out because of this.
In this day an age, it is very hard to find a dependable and honest sitter, so we very highly recommend [name of babysitter] to you.