Use
StackPanel control as your Layout control
Example:
<Window x:Class="WpfApplication2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Name:" VerticalAlignment="Center"/>
<TextBox Width="200"/>
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Age:" VerticalAlignment="Center"/>
<TextBox Width="200"/>
</StackPanel>
</StackPanel>
</Window>