I use my VR3 for primary and use my slates as backup.... In due course I wouldn't mind a 2nd VR3, but for now I rather spend the £££ diving.
I use one of those 3 slate thingies, and cover it in gaffer tape and use a fine permanent marker. My tables are written in much the the same way as others have already stated.
The only difference being, is that the top slate, is actually more of a plan; i.e. I draw out a rough profile, and indicate my descent, depth for gas switch onto BG, when I expect to hit the bottom, total run time at the bottom, and when I'm due to leave, I even show what depth I'm planning on shooting my bag at and TRT when I expect to hit my first deep stop / gas switch.
This is perhaps a bit over kill, but if the shit hits the fan, I want to be able to see my entire dive plane, and not just backup tables.
Sorry that the explanation is a bit convoluted, but if anyone wants, I can post pics.
Cheers
Rich