Apex Callout

In short how to do an apex callout from Class..
Apex class:
*******************************************
global class with sharing ApexCallout{
public void callout()
{
//Construct a HTTP Request
HttpRequest req = new HttpRequest() ;
string strUrl='**********Place your Remote Site Address here**********";
//Before making this callout, you need to add Remote site address in the Remote Site Settings of your Organization..
//Setting Endpoint URL to HTTP request
req.setEndpoint(strUrl);
//Set the request type
req.setMethod('GET');
//HTTP object creation
Http http = new Http();
//Sending the Req throgh HTTPResponse object.
HTTPResponse res = http.send(req);
//System.debug(res.getBody());
//System.debug(res.getStatus());
}
}
If you need to pass some parameters in the method, you can do it..
by changing the method to method with arguments.
You can call this method from trigger also..