I am new in Sharepoint 2010 and up to this point I was working with Sharepoint designer 2010 but it limits my choices so I need to learn how to develop approval workflows in visual studio 2010. I do not want ready made solutions or codes, I need good tutorials to start with. Do you have any proposals of maybe a youtube video, a blog or a site?
Here is a good one: SharePoint 2010: Create a Workflow Activity using Visual Studio 2010:
Try and google:
developing custom workflow actions
developing custom workflow activities
Here is a good general one for SharePoint 2013
Then add SharePoint 2010 to the end of the query, and you can find the ones for 2010.