Might be old school but that's how I was taught.
Board unobtrusively. Ask FA if you can enter flight deck.
Make sure you're not interrupting a checklist or briefing.
Courteously ask for a ride; offer Captain ID, license, Medical & jumpseat form.
If you have to ride up front respect sterile cockpit.
Only pull out your Iphone/ipad/book/magazine if the crew does likewise.
And does it have to be said - no picture taking!