Not minding

Ok so as it states I'm having an issue getting him to mind. My son is 8 and knows plenty well right from wrong. There are two things I simply can't seem to get him to do though

1. I can't get him to ask before he gets into things. If it's my stuff or food or what have you he won't ask may I have blah... or can I have another ... he just does what he wants and waits to get in trouble.

2. I can't leave him alone in the same room as my phone or my laptop. If I so much as walk away in the middle of a project he will get on them and mess everything up.

I've tried grounding him,time out in the corner, taking his stuff away, taking away tv n Xbox time, as well as spanking him. And none of it has gotten his attention. I'm at a loss for what will work.

Any ideas? ?