You can do that one of two ways.
1) Add "Select One" as the first item in your xml and code your listener to ignore that as a selection.
2) Create a custom adapter to insert it as the first line,
EDIT
In your resources
<string-array name="listarray">
<item>Select One</item>
<item>Item One</item>
<item>Item Two</item>
<item>Item Three</item>
</string-array>
In your onItemSelected Listener:
spinnername.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
@Override
public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
if (pos == 0) {
}else {
// Your code to process the selection
}
}
});