Writing Expressions in Search widget: How to write?

How do I write expression to let user search a field..?

Any tips and tricks..?

what type of data should it be? String? Float? Double?

Different expression for different data type?

Field_A like '[value]' ?

Thanks in advance!

Any reference websites is good too, I can't really do it by referring to this site:
http://resources.arcgis.com/en/help/...0000002t000000