public class AuthCallout {

 public void basicAuthCallout(){
 HttpRequest req = new HttpRequest();
 req.setEndpoint('http://www.yahoo.com');
 req.setMethod('GET');

 // Specify the required user name and password to access the endpoint

 // As well as the header and header information


 String username = 'myname';
 String password = 'mypwd';

 Blob headerValue = Blob.valueOf(username + ':' + password);
 String authorizationHeader = 'BASIC ' +
 EncodingUtil.base64Encode(headerValue);
 req.setHeader('Authorization', authorizationHeader);

 // Create a new http object to send the request object

 // A response object is generated as a result of the request


 Http http = new Http();
 HTTPResponse res = http.send(req);
 System.debug(res.getBody());
  }
 }

public static void sendNotification(String name, String city) {

    HttpRequest req = new HttpRequest();
    HttpResponse res = new HttpResponse();
    Http http = new Http();

    req.setEndpoint('http://my-end-point.com/newCustomer');
    req.setMethod('POST');
    req.setBody('name='+EncodingUtil.urlEncode(name, 'UTF-8')+'&city='+EncodingUtil.urlEncode(city, 'UTF-8'));
    req.setCompressed(true); // otherwise we hit a limit of 32000

    try {
        res = http.send(req);
    } catch(System.CalloutException e) {
        System.debug('Callout error: '+ e);
        System.debug(res.toString());
    }

}

// run WebServiceCallout.testMe(); from Execute Anonymous to test
public static testMethod void testMe() {
    WebServiceCallout.sendNotification('My Test Customer','My City');
}

HttpRequest req = new HttpRequest();
HttpResponse res = new HttpResponse();
Http http = new Http();

req.setEndpoint('https://www.mysite.com/myendpoint');
req.setMethod('POST');

//these parts of the POST you may want to customize
req.setCompressed(false);
req.setBody('key1=value1&key2=value2');
req.setHeader('Content-Type', 'application/x-www-form-urlencoded');

try {
    res = http.send(req);
} catch(System.CalloutException e) {
    System.debug('Callout error: '+ e);
}
System.debug(res.getBody());

HttpRequest req = new HttpRequest();
HttpResponse res = new HttpResponse();
Http http = new Http();

req.setEndpoint('callout:My_Named_Credential/some_path');
req.setMethod('POST');
req.setHeader('Content-Type', 'application/x-www-form-urlencoded');
req.setBody('key1=value1&key2=value2');

try {
    res = http.send(req);
    if (res.getStatusCode() == 200) {
        System.debug('Success!');
    } else {
        System.debug('HTTP error: ' + res.getStatusCode());
    }
    System.debug(res.getBody());
} catch(System.CalloutException e) {
    System.debug('Callout error: '+ e);
}