1. How to save/load a report?
2. How to load DataSet XSD schema?
3. How to render a report?
4. How to access to the variables?
5. How to attach data to a report?
6. How to run a report designer?
7. How to save/load a rendered report?
8. How to print a report immediately without preview?

1. How to save/load a report?

To save a report:
StiReport report = new StiReport();
report.Save("report.mrt");
To load a report:
StiReport report = new StiReport();
report.Load("report.mrt");

2. How to load DataSet XSD schema?

To load DataSet XSD schema you may use ImportXMLSchema method:
StiReport report = new StiReport();
DataSet dataSet = new DataSet("Test");
dataSet.ReadXmlSchema("dataset.xsd");
report.Dictionary.ImportXMLSchema(dataSet);

3. How to render a report?

To render a report and to show a rendered report in the preview window:
StiReport report = new StiReport();
report.Load("report.mrt");
report.Show();

4. How to access to the variables?

To access to the variables, you may use this code:
StiReport report = new StiReport();
report.Load("Variables.mrt");
report.Compile();

// Set Variable
report["VariableName"] = "Value";

// Get Variable
object value = report["VariableName"];

5. How to attach data to a report?

It is necessary to register data in the Data Store to attach them to a report. You can do it this way:
DataSet dataSet1 = new DataSet();
dataSet1.ReadXmlSchema("Demo.xsd");
dataSet1.ReadXml("Demo.xml");

StiReport report = new StiReport();
report.RegData(dataSet1);

6. How to run a report designer?

Do it like this:
StiReport report = new StiReport();
report.Design();

7. How to save/load a rendered report?

To save a rendered report:
// Rendering report
StiReport report = new StiReport();
report.Load("report.mrt");
report.Render();

// Saving report
report.SaveDocument("document.mdc");
To load previously saved rendered report:
StiReport report = new StiReport();
report.LoadDocument("document.mdc");

8. How to print a report immediately without preview?

For a start load of a report:
StiReport report = new StiReport();
report.LoadDocument("document.mdc");
And now print a report:
report.Print();