Do you recognize the following? You get a call for support about an issue an user is experiencing. The service desk provides you with some information in the call, but you require more information. Especially, how to reproduce the error? At this point you can do two things. The first is go to the service desk, ask them to call the user and let them figure out what the user is doing  to get the error. The second is, you can call the user yourself and ask them how to reproduce the error.

A problem with both methods is: I am not really good at remembering how applications work, where to click etc, especially if I don't know the application.

Here comes in the ever so handy Problem Step Recorder (psr.exe). You can ask your users to reproduce the problem with PSR enabled and have them attach the recording to the call. This way you won't have to remember how, where and what to click, enter, or whatever. It is well documented and easy to follow.