To invoke an external service after using its WSDL document to generate an Apex class, create an instance of the stub in your Apex script and call the methods on it.

For example, to invoke the StrikeIron IP address lookup service from Apex, you could write a script similar to the following:

// Create the stub
strikeironIplookup.DNSSoap dns = new strikeironIplookup.DNSSoap();

// Set up the license header
dns.LicenseInfo = new strikeiron.LicenseInfo();
dns.LicenseInfo.RegisteredUser = new strikeiron.RegisteredUser();
dns.LicenseInfo.RegisteredUser.UserID = ‘you@company.com’;
dns.LicenseInfo.RegisteredUser.Password = ‘your-password’;

// Make the Web service call
strikeironIplookup.DNSInfo info = dns.DNSLookup(‘www.myname.com’);

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The release of Summer 09 increased the governor limit of a SOAP web service callout request/response size to 1MB from 100KB as can be seen in the Apex documentation here

If you are using the Apex HTTP classes to send web service callouts, the limit is still 100KB. .

The following limits apply when an Apex script makes a callout to an HTTP request or a Web services call. The Web services call can be a Force.com Web Services API call or any external Web services call.

1. A single Apex transaction can make a maximum of 10 callouts to an HTTP request or an API call.
2. The default timeout is 10 seconds. A custom timeout can be defined for each callout. The minimum is 1 millisecond and the maximum is 60 seconds. See the following examples for how to set custom timeouts for Web Services or HTTP callouts.
3. The maximum cumulative timeout for callouts by a single Apex transaction is 120 seconds. This time is additive across all callouts invoked by the Apex transaction.

The following is an example of setting a custom timeout for Web services callouts:

docSample.DocSamplePort stub = new docSample.DocSamplePort();
stub.timeout_x = 2000; // timeout in milliseconds

The following is an example of setting a custom timeout for HTTP callouts:

HttpRequest req = new HttpRequest();
req.setTimeout(2000); // timeout in milliseconds

If you want to migrate from one org to another, then you first need to get a Weekly Export Service download. Make sure you check the “Include attachments” box. You will get an attachments.csv and the actual attachments.

The key to importing attachments is a little known feature inside Data Loader. The part that is not documented is that the import wants the actual filename in the BODY field. So for example, the attachments themselves have a ID name, let’s say its 123456789 and it is on your hard drive in the C:\Export folder. So in the BODY field you need to put C:\Export\123456789.

The only fields you need in the import file are – ParentId, Name, IsPrivate, OwnerId and Body.

Suppose there’s a scenario where in one trigger perform update operation, which results in invocation of second trigger and the update operation in second trigger acts as triggering criteria for trigger one. In that case there will be a recursion and than will be Apex Governor Limits Errors .. bla .. ala .. bla ….

Following are two articles which helps to control or regulate the execution of multiple triggers and prevent recursion.

http://www.tehnrd.com/apex-flow-control-preventing-infinite-loops/

http://blog.jeffdouglas.com/2009/10/02/preventing-recursive-future-method-calls-in-salesforce/

In Visualforce controllers, use ApexPages.currentPage().getHeaders().get(‘Host’) to get the server name (e.g., na1.salesforce.com).