to display the help and let the users easily get help
whenever they need it you can call the Help.ShowHelp
method in your form.

command objects use parameters for passing values
to sql statements for type cheking,validation,guarding
against SQL injection attacks,etc.so its a good practice
to use command parameters to sql statements.

you can use online paypal buy button in your page
for receiving online paypal payment.when users click
this buy button they will enter in payment page
for payment.

It's required that you configure your joomla SMTP settings so that joomla is able to send
email when user registered or different mailing functions works for other components and modules
like k2, CB....
In this post i show how to configure joomla 2.5/3 smtp settings properly.

following are guidelines to develop modules
for dotnetnuke 5/6 with visual studio 2008/2010 -

when you run asp.net application project from visual
studio,visual studio uses their development server.
It's not the right way to develop asp.net appication.