How to enable site collection feature by default when deploying a visual webpart from visual studio?

Hi,

I am making a visual web part in SP 2010 using visual studio 2010.

I want it so that when I add and deploy my wsp file, it should by default keep the site collection feature activated for the web part.

I will be deploying through powershell and central admin only on non-dev environment.

Is there a way to do this? Maybe add some special xml to the feature file?

Also I noticed that the first time I deployed it, it was not active, then I activated the feature. Then from that point, if I ever try to retract and remove, then add and deploy, the feature is activated by default. Can anyone explain whats going on here? I would expect the feature to be inactivated by default...