I'm not an expert in SAP development, I've only developed 2 small apps but I would focus in 2 points: connectivity and data model.
Usually SAP environments are complicated and you can extract data from many places R3 Tables, Infocubes,... where is the data you are going to use? Depending on where is the data you are going to use a specifc SAP Connector or a specific extraction method.
If you are going to access the Database you can use the SAP SQL Connector. Wiht this connector QlikView has developed templates applications for different SAP modules. Each SAP template has 2 different, the 1st app is an extractor that access SAP tables and creates a QV data model and the second a app is a UI. This is the template for SAP FI.
You can take a look in the templates to understand how this specific connector works and to see different SAP modules tables.
You also will need a dictionary. With SAP SQL Connector you can use an app called script builder to access your SAP and build a 'dictionary'. ScripBuilder is provided with the connector, also you can find dictionaries with a good description on SAP data model in the web.
SAP has a functional structure, coorporativa society, a society, accounting structure, a structure of accounts, types of cost. and much more.
SAP is divided into functional modules, MM PP FI CO SD to tell you some.
SAP stores information in tables. and each module has its own tables. Some tables will allow you to link the different modules.
How to know which table is the information. Auxiliate user to identify the report. then put yourself in the field of information and press "F1" key will open a window "Performance Assistant". search and click on the icon called "Technical Info" to change the window, here find the table name and field name.
The "F1" any field work des SAP
Ferran I mention some of the SAP Connector Server
You can take a look at the templates for specific connector understand how this works and to see the tables in different SAP modules.
You will also need a dictionary. With SAP Connector Server that you can use an application called builder script to access the SAP and build a "dictionary". ScripBuilder is supplied with the connector, you can also find dictionaries with a good description of SAP data model on the web.
if you do not have the connector is more complicated.
Tell us how you will make the extraction of data.
our expierience has shown that it depends on our system landscape what connection do you want to use. If you have an existing SAP BW than you should extract your data from the SAP BW. Otherwise you have some further possibilities.
1) Extract your data directly from the SAP tables (It is not possible to extract cluster tables with an SQL command within a JOIN) (SAP offers more than 70.000 database tables)
2) Use SAP Reports/Queries for the extraction of SAP data into QlikView
3) Use a SAP connector that supports the SAP Service API. With such an connector it is possible to use the SAP BW data extractors that offers you an access to the SAP tables and supports also delta load mechanisms, business logic, ... that will be maintained by SAP.The SAP connector from QlikView didn't support the SAP Service API at the time where we introduced QlikView in our hourse. Therefore we use a 3rd party product and it works very well. We have chosen this method and we have good experice with this solution.
I hope it will help you a little bit.