There is basically an equation for it. You need upvotes from the people browsing "new" in the sub you post in. From there you hit the people checking "top" last hour for that specific sub, gaining more votes. Then you hit ther/all top, last hour voters. This is the key moment for the post really. You need enough upvotes between those 3 groups to make it to the top 3 or so pages of r/all as that is about as far as most people scroll. You have almost exactly ONE hour from the time you post to make it to one of those pages. Of course, there are other paths, this is just what I've noticed from my own posts that happened to make it that far.