These 2 simple rules you really don’t want to ignore, unless you don’t care about your sales on Videohive.
I’ll make it short.
1. You always want to make a resolution of your original project file Full HD, which is 1920×1080. Yes, you are going to sweat a little bit more, because this will slow down your workflow and render time. But in the end.. why not to spend some time more on making a product now, rather than seeing less sales after? Which is better?
2. You always want to make a project file compatible with After Effects versions CS3, CS4, CS5, CS5.5 and the ones that will come out after. Yes, workflow in CS3 is a little bit slower, than in CS5.5. But inspite of that, you get almost the same visual results. I’d even say, that visual results are totally identical. And yes, if you have only CS5 right now, you will have to get CS3.